Cd200 inhibitors and methods of use thereof

ABSTRACT

The present invention provides in certain embodiments conjugates comprising at least one CD200 inhibitor and an adjuvant, and methods of reversing or modulating immune suppression in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition comprising a CD200 inhibitor and an adjuvant.

PRIORITY OF INVENTION

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 62/019,206, which was filed on Jun. 30, 2014, which is incorporated by reference herein.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jul. 14, 2015, is named 09531.386US1_SL.txt and is 3,479 bytes in size.

BACKGROUND OF THE INVENTION

Despite advances in cancer research, there are still no adequate treatments for many cancers. For example, malignant glioma is a devastating disease that arises in over 14,000 patients a year in the United States. Due to the ability of glioma cells to migrate several centimeters from the bulk tumor cavity, current standard of care only has marginal improvements, with a 5-year survival below 30%. Patients with glioblastoma exhibit systemic immune suppression resulting in deficient adaptive immune responses. These deficiencies' are due to the enriched immunosuppressive factors secreted by the tumor suppressing T cell proliferation and cytotoxic function. Immunosuppression plays an important role in tumor progression in patients with glioblastoma. If the immune suppression could be reversed allowing an effective immune targeting, then patients with glioma will have less tumor progression and improved outcomes.

Accordingly, new compositions and methods to treat cancer are needed. In particular, new compositions that reverse the immunologically suppressed microenvironment caused by tumors are needed.

SUMMARY OF THE INVENTION

The present invention provides in certain embodiments a conjugate comprising at least one CD200 inhibitor operably linked to an adjuvant.

In certain embodiments, the CD200 inhibitor is a peptide having a length of 5 to 20 amino acids.

In certain embodiments, the peptide is 90% identical to amino acid sequence SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:8 or SEQ ID NO:9.

In certain embodiments, one of the amino acids in SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:8 or SEQ ID NO:9 is substituted with an alanine.

In certain embodiments, the adjuvant is a toll-like receptor (TLR) ligand.

In certain embodiments, the adjuvant is a CpG ODN, Annexin A2, or Poly ICLC, or a fragment thereof.

In certain embodiments, the adjuvant is a fragment Annexin A2, and the fragment of Annexin A2 is the first 12-100 amino acid residues of the N-terminus of Annexin A2 (i.e., any number in between 12 and 100, such as 12, 13, 14, . . . 98, 99, 100). In certain embodiments, the adjuvant is a fragment Annexin A2, and the fragment of Annexin A2 is the first 12-50 amino acid residues of the N-terminus of Annexin A2. In certain embodiments, the adjuvant is a fragment Annexin A2, and the fragment of Annexin A2 is the first 12-20 amino acid residues of the N-terminus of Annexin A2. In certain embodiments, the adjuvant is a fragment Annexin A2, and the fragment of Annexin A2 is the first 15 amino acid residues of the N-terminus of Annexin A2. In certain embodiments, the adjuvant is MSTVHEILCKLSLEG (SEQ ID NO: 10).

In certain embodiments, the adjuvant is linked to the CD200 inhibitor by means of a covalent bond.

In certain embodiments, the adjuvant is linked to the CD200 inhibitor by means of a linking group. In certain embodiments, the linking group comprises one or more amino acid residues. In certain embodiments, the linking group is a peptide having from one to four amino acid groups. In certain embodiments, the linking group comprises a chemical linker.

In certain embodiments, the chemical linker utilizes an acetamide linkage or a maleimide linkage.

The present invention provides in certain embodiments a composition comprising a conjugate as described above and a pharmaceutically acceptable carrier or diluent.

In certain embodiments, the composition further comprises at least one additional CD200 inhibitor.

In certain embodiments, the composition further comprises a cancer vaccine. In certain embodiments, the cancer vaccine is a tumor lysate. In certain embodiments, the tumor lysate is substantially devoid of CD200. As used herein “substantially devoid” means that the substance (e.g., tumor lysate) has a diminished level of D200, e.g., between 1-100% less CD200 than an unprocessed substance. In certain embodiments, the CD200 is removed by absorption using standard methods.

In certain embodiments, the composition is formulated for oral administration or injection.

In certain embodiments, the composition is formulated for use in a method of treatment of a human or animal body for therapy.

In certain embodiments, the composition further comprises an adjuvant not linked to the conjugate.

In certain embodiments, the composition further comprises a cancer therapy.

In certain embodiments, the composition described above is used in the manufacture of a medicament for treating a disease or disorder arising from abnormal cell growth, function or behavior. In certain embodiments, the disease or disorder is cancer. In certain embodiments, the cancer is selected from solid tumors of the colon, breast, brain, liver, ovarian, gastric, lung, and head and neck. In certain embodiments, the cancer is selected from glioblastoma, melanoma, prostate, endometrial, ovarian, breast, lung, head and neck, hepatocellular, and thyroid cancers. In certain embodiments, the cancer is selected from breast, ovary, cervix, prostate, testis, genitourinary tract, esophagus, larynx, glioblastoma, neuroblastoma, stomach, skin, keratoacanthoma, lung, epidermoid carcinoma, large cell carcinoma, non-small cell lung carcinoma (NSCLC), small cell carcinoma, lung adenocarcinoma, bone, colon, adenoma, pancreas, adenocarcinoma, thyroid, follicular carcinoma, undifferentiated carcinoma, papillary carcinoma, seminoma, melanoma, sarcoma, bladder carcinoma, liver carcinoma and biliary passages, kidney carcinoma, myeloid disorders, lymphoid disorders, hairy cells, buccal cavity and pharynx (oral), lip, tongue, mouth, pharynx, small intestine, colon-rectum, large intestine, rectum, brain and central nervous system, Hodgkin's lymphoma and leukemia.

In certain embodiments, the present invention provides a method of treating a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to an animal in need thereof a therapeutic regimen comprising a composition as defined above. In certain embodiments, the therapeutic regimen is administered at least twice. In certain embodiments, the administration comprises administering at least three doses of the therapeutic regimen. In certain embodiments, the administration comprises administering at least five doses of the therapeutic regimen. In certain embodiments, the administration comprises administering at least ten doses of the therapeutic regimen. In certain embodiments, the administration comprises administering at least two consecutive dosages of the administration are separated by an interval of about one week. In certain embodiments, at least two consecutive dosages of the administration are separated by an interval of about one month.

In certain embodiments, the method comprises further administering an adjuvant before, concurrently or after administration of the therapeutic regimen.

In certain embodiments, the present invention provides a method of reversing or modulating immune suppression in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition described above.

In certain embodiments, the present invention provides a method of reversing or modulating immune suppression in a tumor microenvironment or sentinel lymph nodes in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition described above.

In certain embodiments, the present invention provides a method of enhancing efficacy of a cancer vaccine in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition described above.

In certain embodiments, the disease or disorder is cancer. In certain embodiments, the cancer is selected from glioblastoma, melanoma, prostate, endometrial, ovarian, breast, lung, head and neck, hepatocellular, and thyroid cancers. In certain embodiments, the cancer is selected from breast, ovary, cervix, prostate, testis, genitourinary tract, esophagus, larynx, glioblastoma, neuroblastoma, stomach, skin, keratoacanthoma, lung, epidermoid carcinoma, large cell carcinoma, non-small cell lung carcinoma (NSCLC), small cell carcinoma, lung adenocarcinoma, bone, colon, adenoma, pancreas, adenocarcinoma, thyroid, follicular carcinoma, undifferentiated carcinoma, papillary carcinoma, seminoma, melanoma, sarcoma, bladder carcinoma, liver carcinoma and biliary passages, kidney carcinoma, myeloid disorders, lymphoid disorders, hairy cells, buccal cavity and pharynx (oral), lip, tongue, mouth, pharynx, small intestine, colon-rectum, large intestine, rectum, brain and central nervous system, Hodgkin's lymphoma and leukemia. In certain embodiments, the animal is a human.

In certain embodiments, the present invention provides a process for producing a pharmaceutical composition comprising combining in the composition described above with a pharmaceutically acceptable carrier.

In certain embodiments, the present invention provides a kit for treating cancer, comprising: (a) a first pharmaceutical composition comprising a composition described above; and (b) instructions for use.

In certain embodiments, the present invention provides a nucleic acid molecule encoding a CD200 inhibitor linked to an adjuvant.

In certain embodiments, the present invention provides an expression cassette comprising the molecule described above.

In certain embodiments, the expression cassette further comprises a promoter.

In certain embodiments, the present invention provides a viral vector comprising the expression cassette described above.

In certain embodiments, the vector is an adenovirus (Ad). In certain embodiments, the Adenovirus is Ad5.

In certain embodiments, the delivering comprises administering the composition to the animal intravenously.

In certain embodiments, the composition is administered to the animal using a systemic pump.

In certain embodiments, the method further comprises administering a chemotherapy agent. In certain embodiments, the chemotherapy agent is sunititib, ontak, cyclophosphamide, gemcitabine, and/or retionoic acid.

The present invention provides a composition comprising at least one CD200 inhibitor. In certain embodiments, the composition further comprises a cancer vaccine. In certain embodiments, the cancer vaccine is a tumor lysate. In certain embodiments, the tumor lysate is substantially devoid of CD200. In certain embodiments, the CD200 inhibitor is a peptide that has a length of 5 to 20 amino acids. In certain embodiments, the peptide is 90% identical to amino acid sequence SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:8 or SEQ ID NO:9. In certain embodiments, one of the amino acids in SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:8 or SEQ ID NO:9 is substituted with an alanine. In certain embodiments, the peptide has the amino acid sequence of SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:8 or SEQ ID NO:9.

The present invention in certain embodiments provides a pharmaceutical composition which comprises a pharmaceutically acceptable carrier or diluent and, as an active ingredient, a CD200 inhibitor as described above. In certain embodiments, the pharmaceutical composition is formulated for oral administration or injection. In certain embodiments, the pharmaceutical composition is used in a method of treatment of a human or animal body for therapy. In certain embodiments, the composition further comprises a cancer therapy.

The present invention in certain embodiments provides a use of a composition as defined above for use or in the manufacture of a medicament for treating a disease or disorder arising from abnormal cell growth, function or behavior. In certain embodiments, the disease or disorder is cancer. In certain embodiments, the cancer is selected from solid tumors of the colon, breast, brain, liver, ovarian, gastric, lung, and head and neck. In certain embodiments, the cancer is selected from glioblastoma, melanoma, prostate, endometrial, ovarian, breast, lung, head and neck, hepatocellular, and thyroid cancers. In certain embodiments, the cancer is selected from breast, ovary, cervix, prostate, testis, genitourinary tract, esophagus, larynx, glioblastoma, neuroblastoma, stomach, skin, keratoacanthoma, lung, epidermoid carcinoma, large cell carcinoma, non-small cell lung carcinoma (NSCLC), small cell carcinoma, lung adenocarcinoma, bone, colon, adenoma, pancreas, adenocarcinoma, thyroid, follicular carcinoma, undifferentiated carcinoma, papillary carcinoma, seminoma, melanoma, sarcoma, bladder carcinoma, liver carcinoma and biliary passages, kidney carcinoma, myeloid disorders, lymphoid disorders, hairy cells, buccal cavity and pharynx (oral), lip, tongue, mouth, pharynx, small intestine, colon-rectum, large intestine, rectum, brain and central nervous system, Hodgkin's lymphoma and leukemia.

The present invention in certain embodiments provides a method of treating a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a therapeutic regimen comprising a composition as defined above or a cancer vaccine and a CD200 inhibitor administered sequentially. In certain embodiments, the therapeutic regimen is administered at least twice. In certain embodiments, the therapeutic regimen is administered at least three doses of the therapeutic regimen. In certain embodiments, the administration comprises administering at least five doses of the therapeutic regimen. In certain embodiments, the administration comprises administering at least ten doses of the therapeutic regimen. In certain embodiments, at least two consecutive dosages of the administration are separated by an interval of about one week, or about one month. In certain embodiments, the method further comprises administering an adjuvant before, concurrently or after administration of the therapeutic regimen.

In certain embodiments, the present invention comprises a method of reversing or modulating immune suppression in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof the composition or therapeutic regimen described above.

In certain embodiments, the present invention comprises a method of reversing or modulating immune suppression in a tumor microenvironment or sentinel lymph nodes in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof the composition or therapeutic regimen described above. In certain embodiments, the disease or disorder is cancer. In certain embodiments, the cancer is selected from glioblastoma, melanoma, prostate, endometrial, ovarian, breast, lung, head and neck, hepatocellular, and thyroid cancers.

In certain embodiments, the cancer is selected from breast, ovary, cervix, prostate, testis, genitourinary tract, esophagus, larynx, glioblastoma, neuroblastoma, stomach, skin, keratoacanthoma, lung, epidermoid carcinoma, large cell carcinoma, non-small cell lung carcinoma (NSCLC), small cell carcinoma, lung adenocarcinoma, bone, colon, adenoma, pancreas, adenocarcinoma, thyroid, follicular carcinoma, undifferentiated carcinoma, papillary carcinoma, seminoma, melanoma, sarcoma, bladder carcinoma, liver carcinoma and biliary passages, kidney carcinoma, myeloid disorders, lymphoid disorders, hairy cells, buccal cavity and pharynx (oral), lip, tongue, mouth, pharynx, small intestine, colon-rectum, large intestine, rectum, brain and central nervous system, Hodgkin's lymphoma and leukemia.

In certain embodiments, the present invention provides a method, wherein the delivering comprises administering the composition to the animal intravenously.

In certain embodiments, the present invention provides a method wherein the composition is administered to the animal using a systemic pump.

In certain embodiments, the present invention further provides administering a chemotherapy agent. In certain embodiments, the chemotherapy agent is sunititib, ontak, cyclophosphamide, gemcitabine, and/or retionoic acid.

In certain embodiments, the animal is a human.

In certain embodiments, the present invention provides process for producing a pharmaceutical composition comprising combining in the composition described above with a pharmaceutically acceptable carrier.

In certain embodiments, the present invention provides a kit for treating cancer, comprising (a) a first pharmaceutical composition comprising a composition described above; and (b) instructions for use.

In certain embodiments, the present invention provides a nucleic acid molecule encoding a CD200 inhibitor, wherein the inhibitor is a peptide.

In certain embodiments, the present invention provides expression cassette comprising provides a nucleic acid molecule encoding a CD200 inhibitor, wherein the inhibitor is a peptide. In certain embodiments, the expression cassette further comprises a promoter.

In certain embodiments, the present invention provides a viral vector comprising the expression cassette described above. In certain embodiments, the vector is an adenovirus (Ad), such as Ad5.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1. Illustration of CD200 (OX-2) interaction with OX2R.

FIGS. 2A-B. A) Vaccination scheme. Tumor bearing or non-tumor bearing mice were vaccinated on day 2 and 8 with an agonist (4012) or antagonist (6059) only, and on days 3-6 and 10 with OVA+Poly:ICLC+/− the competitive inhibitor 6059 (antagonist of a agonist). B) Mice were bled on day 10, whole blood was stained with an anti-CD8 and SIINFEKL (SEQ ID NO: 11) specific detramer, lysed and analyzed by flow cytometry. This experiment demonstrated that the competitive inhibitor (antagonist) reversed the suppressive effects of the tumor microenvironment.

FIGS. 3A-B. Tumor bearing or non-tumor bearing mice were vaccinated on day 2 and 8 with an agonist or antagonist only, and on days 3-6 and 10 with OVA+Poly:ICLC+/− the competitive inhibitor 6059 (antagonist of a agonist). On day 10, were harvested and stimulated with OVA protein to measure a recall response via cytokine release. A) TNF alpha (PG/ML) levels from tumor bearing mice. B) INF gamma (PG/ML) levels in tumor bearing mice. This experiment demonstrated that the competitive inhibitor reversed the suppressive effects of the tumor microenvironment.

FIGS. 4A-C. A) GL261 tumor bearing mice were inoculated with 50 μg of antagonist 6059 one day prior to vaccination with tumor lysate (65 μg)+/−the antagonist 6059 (50 μg). B) Mice were imaged weekly for tumor growth. The following groups were studied: saline (1), tumor lysate (2), and tumor lysate+6059 (3). C) Percent survival post inoculation for saline (1), tumor lysate (2), and tumor lysate+6059 (3) groups. This experiment demonstrated that the use of our competitive inhibitor slowed tumor growth enhancing survival by 30%.

FIGS. 5A-B. A) GL261 tumor bearing mice were inoculated with 10 μg of 6059 on day 2 into the tumor site then with 50 μg of antagonist 6059 one day prior to vaccination with tumor lysate (65 μg)+ the antagonist 6059 (50 μg). B) Mice were imaged weekly for tumor growth. The following groups were studied: saline (1), tumor lysate+6059 (2), and CNS+tumor lysate+6059 (3) groups. Inoculating mice in the CNS further suppressed tumor growth demonstrating a reversal of tumor induced suppression in the CNS.

FIG. 6. Percent survival of mice inoculated with 1×10⁶ EMT6 cells. To determine if our competitive inhibitors worked in other tumor models, mice were inoculated in the fat pad with 1×10⁶ EMT6 cells. Specifically, mice were vaccinated with 65 μg of EMT6 tumor lysates+50 μg of adjuvant CpG and 50 μg of different completive inhibitors (6059, 4004, 4013 and 6061) and monitored for survival. Saline and tumor lysate+adjuvant CpG were used as controls. This experiment determined that the competitive inhibitors significantly extended survival benefit in our breast carcinoma model.

FIG. 7. Scheme for suppressive effects of soluble CD200: dendritic cells take up tumor antigen at the injection site and migrate to local draining lymph nodes where they are susceptible to the suppressive effects of soluble CD200 thereby altering T cell functions.

FIG. 8. Scheme illustrating consistent delivery of CD200 inhibitors in the CNS, which will prevent CD200-mediated immunosuppression in the tumor microenvironment by removing CD200 from the CD200 receptor blocking any further binding.

FIGS. 9A-B. Vaccination scheme of tumor bearing and non-tumor bearing mice. Mice were bled on day 7, whole blood was stained with an anti-CD8 and SIINFEKL (SEQ ID NO: 11) specific detramer, lysed and analyzed by flow cytometry.

FIG. 10. In vivo survival study. Four groups were studied: (1) Saline; (2) Tumor lysate; (3) Tumor Lysate+6059; (4) Pretreated mice with 6059 only 2 days prior to vaccination with tumor lysate+6059. All vaccinations were administered in the back of the neck in tumor bearing mice.

FIGS. 11A-B. Splenocytes were pulsed with OVA+an inhibitor peptide and incubated for 24 h. Following incubation, cells were washed, purified OT1 were added to wells and incubated for an additional 48 hrs then analyzed for A) TNFa and IL-6 production; and B) IL-2 and IL-17 production. Error bars indicate +/−SEM (n=4/group; *P<0.05; ** P<0.01).

FIGS. 12A-C. CD200R antagonist reverses the suppressive effects of the tumor environment. Tumor and non-tumor bearing mice were vaccinated with OVA+Poly:ICLC+/− the CD200R antagonist 6059 and analyzed for A) SIINFEKL/Kb⁺CD8⁺ T cell expansion (‘SIINFEKL’ disclosed as SEQ ID NO: 11). B) Lymphocytes were harvested and stimulated with SIINFEKL peptide (SEQ ID NO: 11). Supernatants were analyzed for TNFα and IFNγ secretion. C) The antagonist 6059 was added to OVA+exosomes. Error bars indicate +/−SEM (n=4/group; *P<0.05; by t-test). FIG. 12 discloses ‘SIINFEKL’ disclosed as SEQ ID NO: 11.

FIGS. 13A-B. CD200R antagonist enhances survival. Mice were inoculated with A) GL261 or B) EMT6 breast carcinoma cells and vaccinated with autologous tumor lysates plus various antagonists and monitored for survival.

FIG. 14. Vaccination scheme: inoculation of wildtype mice with GL261 cells.

FIGS. 15A-C. Brain tumors express CD200. (A) Western analysis of CD200 on Anaplastic oligoastrocytoma; AO, Glioblastoma Multiforme; GBM, Meningioma; (MEN), Ependymoma; EPN, Oligodendroglioma; ODG and Pilocytic Astrocytoma; PA. (B) mRNA CD200 expression levels on Rhabdomysarcoma; RMS were compared to Glioblastoma Multiforme; GBM, Anaplastic Astrocytoma; AA, Pilocytic Astrocytoma; PA, Anaplastic Oligoastrocytoma; AO, Oligodendrogliomas; ODG, Primitive Neuroectodermal; PNET, Medulloblastoma; MED, Ependymoma; EPD and Craniopharyngioma; CRP. (C) mRNA CD200 expression levels on Proneural; PRO Glioblastoma Multiforme subsets compared to Proliferative; Prolif, Mesenchymal; Mes and Promesenchymal; Promes. Means are indicated, statistical significance was determined by one-way ANOVA, post hoc analysis by Dunn's multiple comparison test, *p<0.05, ** p<0.001, *** p<0.0001.

FIGS. 16A-B. Soluble CD200 in GBM patients correlated with MDSC expansion. (A) Serum concentrations of soluble CD200 were analyzed from patients bearing Anaplastic Oligoastrocytoma; AO, Anaplastic Astrocytoma; AA, Ependymoma; EPD, Medulloblastoma; MED, Meningioma; MEN and healthy donors; HD. (B) Serum concentration of soluble CD200 from patients bearing glioblastoma multiforme was correlated to expansion of lineage negative MDSC population. Means are indicated, statistical significance was determined by one-way ANOVA, post hoc analysis by Dunn's multiple comparison test, *p<0.05, ** p<0.001,

FIGS. 17A-B. CD200R antagonist blocks MDSC expansion and tumor suppressive effects. (A) Murine glioma GL261 was incubated with naïve splenocytes in a trans-well plate+/−CD200R antagonist and analyzed for MDSC expansion and cytokine production. (B) Naïve splenocytes were pulsed with purified CD200+/−CD200R antagonist and analyzed for MDSC expansion and arginase-I production. Error bars are ±SEM, statistical significance was determined by one-way ANOVA, post hoc analysis by Dunn's multiple comparison test, *p<0.05, ** p<0.001.

FIGS. 18A-D. CD200R antagonist blocks CD200 induced immune suppression enhancing survival. (A & B) Tumor bearing mice were vaccinated with OVA+Poly:ICLC+/−antagonist then analyzed for OVA-specific T cells and cytokine production following in vitro restimulation with OVA. Tumor bearing mice were vaccinated with saline (n=10), tumor lysate+CpG (n=10) or tumor lysate+CpG+antagonist 6059 (n=10). (C) Mice were imaged weekly for tumor growth and (D) followed for survival. Error bars are ±SEM, *p<0.05, ** p<0.001 was determined by one-way ANOVA, post hoc analysis by Dunn's multiple comparison test, log-rank analysis was used for survival.

FIGS. 19A-B. Select CD200 antagonists enhance survival. (A) EMT6 tumor bearing mice were vaccinated with tumor lysate, CpG+/−CD200 antagonist 4004, 4013 or 6059. (B) New CD200R antagonist P1-A12 enhances survival. Log-rank analysis was used for survival.

FIG. 20. Comparison of CD200 mRNA expression on ependymoma and Medulloblastoma tumor subsets. (A) CD200 mRNA expression levels were compared between Ependymoma subsets Posterior Fossa A (PFA), Posterior Fossa B (PFB), Supratentorial (ST) and Medulloblastoma subsets Sonic Hedgehog positive (SHH⁺) compared to group 3 (cMYC⁺) and group 4 (Sonic Hedgehog negative/cMYC negative (SHI-FcMYC)) subsets. Means are indicated, statistical significance was determined by one-way ANOVA, post hoc analysis by Dunn's multiple comparison test, *p<0.05, ** p<0.001, *** p<0.0001.

FIGS. 21A-B. Variable tissue expression of CD200. (A) mRNA expression levels of CD200 from indicated tissues were analyzed by microarray. (B) mRNA expression levels of CD200 from different regions of normal brains were analyzed by microarray. Means are indicated, statistical significance was determined by one-way ANOVA, post hoc analysis by Dunn's multiple comparison test, *p<0.05, ** p<0.001, *** p<0.0001.

FIGS. 22A-B. Comparison of soluble CD200 post-vaccination.

FIG. 23. CD200 inhibitor inhibits MDSC expansion in vivo. Mice were vaccinated as described in FIG. 4 with peptide inhibitor P1A12. Blood from mice vaccinated with tumor lysate+CpG or tumor lysate+CpG+inhibitor were analyzed for MDSC expansion.

FIG. 24. CD200 inhibitor acts as an agonist for the CD200 receptor. CD11b cells isolated for wild type or CD200 receptor knock out mice were pulsed with OVA+Poly:ICLC+/−P1A12 inhibitor. Scrambled inhibitor was use as a control. Cells were washed and OT-I Cells were added. A. Supernatants were analyzed for IFN gamma following 48 hour incubation.

FIG. 25. CD200 inhibitor enhances Chemotaxis. Non-tumor bearing mice were vaccinated saline, tumor lysate or inhibitor.

FIGS. 26A-D. CD200 inhibitor enhances Chemotaxis. Results from scheme set forth in FIG. 25. Twenty four hours later, mice were vaccinated with A) Saline B) Tumor lysate (TL)+CpG or C) Tumor lysate+CpG+agonist. Six hours later, injection site (skin) was harvested and analyzed for lymphocyte infiltration. D. Lymphocytes within 8 layers of skin/treatment groups were counted to determine enhanced lymphocyte infiltration.

FIG. 27. CD200 inhibitor enhances Co-Stimulatory molecule expression. Purified CD11b cells were pulsed with OVA or OVA+inhibitor. Cells were harvested 48 hours later and analyzed for HLA-DR and co-stimulation markers CD80 and CD86 expression.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that the interaction of CD200 and CD200-Receptor (CD200R) creates an immune-suppressive tumor microenvironment. It has also been found that soluble CD200 enhances inhibition of leukocytes in the tumor microenvironment. Further, higher expression of CD200 on tumor cells is correlated to malignancies.

The present invention provides conjugate comprising a CD200 inhibitor operably linked to an adjuvant.

CD200 Inhibitors

As used herein an antagonist of CD200 is also referred to as a competitive inhibitor of CD200. In certain embodiments a CD200 inhibitor binds to CD200R, which is a receptor for CD200. In certain embodiments, the CD200 inhibitor prevents CD200 from binding to CD200R.

In certain embodiments a CD200 inhibitor may be a peptide. In certain embodiments, the CD200 inhibitor is a peptide that has a length of 5 to 20 amino acids. For example, in certain embodiments, the peptide is 5, 6, 7, 8, 9, 10, 11, 12, 13 14, 15, 16, 17, 18, 19 or 20 amino acids in length.

In certain embodiments, the peptide may correspond to a domain of CD200. Gorczynski et al. described specific regions of the CD200 protein which act as antagonists (J. Surg. Res 2008; 145(1): 87-96). Thus, in certain embodiments, the CD200 inhibitor may be a peptide described in Gorczynski et al. J. Surg. Res 2008; 145(1): 87-96. In certain embodiments, the CD 200 inhibitor is one of the following:

CD200 Inhibitor Peptide Sequence Antagonist 6059 NTIGDGGCY (SEQ ID NO: 1) Antagonist 6061 RCSLKTSQE (SEQ ID NO: 2) Antagonist 4004 TASLRCSLKTSQE (SEQ ID NO: 3) Antagonist 4013 LFNTFGSQKVSGT (SEQ ID NO: 4) Antagonist 4006 SQKVSGTACLTLY (SEQ ID NO: 5) Antagonist C-A12 VTWQKKKAVSPANM (SEQ ID NO: 8) Antagonist 6059C-A NTIGDGGAY (SEQ ID NO: 9)

In certain embodiments, the CD200 inhibitor peptide contains a substitution of one or more amino acids, such as with an alanine. For example, Antagonist 6059 can be substituted at the eighth reside with an alanine. In certain embodiments, the CD200 inhibitor peptide is Antagonist C-A12 or Antagonist 6059C-A.

Additionally, in other embodiments of the invention, a CD200 inhibitor may be one described in Kretz-Rommel, Journal of Immunology, 2008, 699-705; Chen, International Immunology, 17(3), 289-296 (2005); Gorczynski, International Scholarly Research Network, ISRN Immunology, Volume 2012, Article ID 682168; pages 1-18; US Patent Publication No. 2002/0168364; U.S. Pat. No. 6,955,811; or U.S. Pat. No. 7,902,151.

As used herein, an agonist of CD200 has an equivalent biological effect as CD200. Certain CD200 agonists have been previously described, for example by Gorczynski et al. J. Surg. Res 2008; 145(1): 87-96, including agonist 4005 (SPENMVTYSKT (SEQ ID NO:6)) and agonist 4012 (TYSKTHGVVTQ (SEQ ID NO:7)).

Adjuvants

An “adjuvant” is a molecule or compound that nonspecifically stimulate the humoral and/or cellular immune response. They are considered to be nonspecific because they only produce an immune response in the presence of an antigen. Adjuvants allow much smaller doses of antigen to be used and are essential to inducing a strong antibody response to soluble antigens. For example, when a therapeutic agent is administered in conjunction with an adjuvant, the therapeutic agent can be administered before, after, and/or simultaneously with the adjuvant.

In certain embodiments, the composition or conjugate comprises an adjuvant. In certain embodiments, the adjuvant is a toll-like receptor ligand, such as CpG ODN, Annexin A2, Poly ICLC, or non-TLR ligands that stimulate immune responses.

In certain embodiments, the adjuvant used in the present invention is a TLR ligand. In certain embodiments, the adjuvant is a TLR2 ligand. In certain embodiments, the TLR2 ligand is Annexin A2 (a protein) or a fragment of Annexin A2. In certain embodiments, the fragment of Annexin A2 is the first 10-100 amino acid residues of the N-terminus of Annexin A2. In certain embodiments, the fragment of Annexin A2 is the first 12-20 amino acid residues of the N-terminus of Annexin A2. In certain embodiments, the fragment of Annexin A2 is the first 15 amino acid residues of the N-terminus of Annexin A2. In certain embodiments, the fragment is MSTVHEILCKLSLEG (SEQ ID NO: 10).

In certain embodiments, additional or alternative adjuvants include, but are not limited to, Imiquimod, surfactants, e.g., hexadecylamine, octadecylamine, lysolecithin, dimethyldioctadecylammonium bromide, N,N-dioctadecyl-N′—N-bis(2-hydroxyethyl-propane di-amine), methoxyhexadecyl-glycerol, and pluronic polyols; polanions, e.g., pyran, dextran sulfate, poly IC, polyacrylic acid, carbopol; peptides, e.g., muramyl dipeptide, aimethylglycine, tuftsin, oil emulsions, alum, and mixtures thereof. Other potential adjuvants include the B peptide subunits of E. coli heat labile toxin or of the cholera toxin. McGhee, J. R., et al., “On vaccine development,” Sem. Hematol., 30:3-15 (1993). Finally, the immunogenic product may be incorporated into liposomes for use in a formulation, or may be conjugated to proteins such as keyhole limpet hemocyanin (KLH) or human serum albumin (HSA) or other polymers.

In certain embodiments, the composition or conjugate is conjugated to a carrier such as a dendritic cell or a macrophage. In certain embodiments, the composition is contained in a non-cell carrier, such as a liposome.

Linking Group

In certain embodiments, adjuvant is operably linked to the CD200 inhibitor by means of a linking group. In certain embodiments, the linking group comprises one or more amino acid residues.

In certain embodiments, the linking group is a chemical linking group. In certain embodiments, the chemical linker utilizes an acetamide linkage or a maleimide linkage.

In certain embodiments the linking group is about 400-1000 daltons or about 3-12 angstroms in length. The linking group useful in the present invention must be at least bivalent so that they can covalently join two molecules, the adjuvant to CD200 inhibitor. In certain embodiments, the cross-linker can be tris-succinimidyl aminotriacetate (TSAT); bis(sulfosuccinimidyl) suberate (BS³); disuccinimidyl suberate (DSS); bis (2-[sulfosuccinimidyooxycarbonloxy]ethylsulfone) (BOSCOES); bis(2-[succinimidyooxycarbonloxy]ethylsulfone) (Sulfo-BOSCOES); ethylene glycol bis-(succinimidylsuccinate) (EGS); ethylene glycol bis-(sulfosuccinimidylsuccinate) (Sulfo-EBS); or Dimethyl 3,3′-dithiobis-propionimidate (DTBP). In certain embodiments, the linking group is trivalent (such as TSAT). In certain embodiments of the present invention, a single molecule of adjuvant is covalently bound to a single CD200 inhibitor molecule by means of a single linking group molecule. The single linking group molecule can be, for example, bivalent or trivalent.

Methods for utilizing linking group are well known in the art (cf. Hermanson, 1995 Bioconjugate Techniques, Academic Press, Inc. New York, pp. 728; Wong, 1991 Chemistry of Protein Conjugation and Cross-linking. CRC Press, pp. 340; Brinkley, 1992 A brief survey of methods for preparing protein conjugates with dyes, haptens and cross-linking reagents Bioconjugate Chem. 3:2-13).

Conjugates

In certain embodiments, the present invention provides a CD200 inhibitor peptide operably linked to an adjuvant. In certain embodiments, the adjuvant is conjugated to the CD200 inhibitor peptide by covalent bonds.

In certain embodiments, the adjuvant is conjugated to a CD200 inhibitor peptide by means of a chemical linker.

In certain embodiments, the present invention is a CD200 inhibitor peptide conjugated to a fragment of Annexin A2. In certain embodiments, the present invention provides Antagonist C-A12 or Antagonist 6059C-A conjugated to an adjuvant, such as a fragment of Annexin A2. In certain embodiments, the fragment is MSTVHEILCKLSLEG (SEQ ID NO: 10). In certain embodiments, the conjugate is Antagonist C-A12 linked to MSTVHEILCKLSLEG (SEQ ID NO: 10).

In certain embodiments, a CD200 inhibitor or a composition or conjugate as described herein comprising a CD200 inhibitor may be used to reverse or modulate immune suppression. CD200 is an immunosuppressive protein that negatively regulates immune cells bearing the CD200R (e.g., suppresses antigen-specific CD8⁺ T cell responses). As described herein, “reversing or modulating immune suppression” refers to altering, impeding, reducing the immunosuppressive properties of the CD200 protein and/or tumor. In certain embodiments, the CD200 protein activity is reduced in a mammal by 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% as compared to the activity on the tumor in the absence of the CD200 protein. For example, immunosuppressive cells, such as myeloid-derived suppressor cells and regulatory T cells show increased activity while dendritic cells (DCs) appear to be impaired in tumors and sentinel lymph nodes in cancer patients. Accordingly, in certain embodiments, administration of a CD200 inhibitor or a composition as described herein comprising a CD200 inhibitor could decrease the activity of immunosuppressive cells, such as myeloid-derived suppressor cells and regulatory T cells and/or could increase the activity of DCs in the tumor microenvironment and/or sentinel lymph nodes. In certain embodiments, reversal or modulation could be ascertained by assessing cytokine profiles as described herein (e.g., cytokine profiles could be determined before and after administration of a CD200 inhibitor and compared; see also, the Examples).

As referred herein, the “tumor microenvironment” is the normal cells, molecules and blood vessels that surround and feed a tumor cell. A tumor can change its microenvironment and the microenvironment can affect how a tumor grows and spreads.

Cancer Vaccine

As described herein, a cancer vaccine may be a tumor antigen vaccine. Tumor antigen vaccines are vaccines made of cancer cells (e.g, tumor lysate), parts of cancer cells, or pure tumor antigens (substances isolated from tumor cells). A tumor antigen vaccine may stimulate the body's immune system to find and kill cancer cells. For example, the cancer vaccine may comprise glioma cancer cells, breast cancer cells, or other solid tumor cancer cells, or parts of these cells or antigens derived from these cells. In certain embodiments, the cancer vaccine comprises a vaccine antigen, wherein cultured tumor cell derived lysates are the source of the antigen.

In certain embodiments, the cancer vaccine may be a GL261-derived vaccine. In certain embodiments, the cancer vaccine comprises a peptide containing an OVA-derived SIINFEKL (SEQ ID NO: 11) epitope. In certain embodiments the peptide is EVSQLEQLESIINFEKLTEEWTSSNVM (SEQ ID NO: 12).

In certain embodiments, a CD200 inhibitor or a conjugate comprising a CD200 inhibitor enhances the efficacy of a cancer vaccine (e.g., when administered simultaneously or sequentially). For example, in certain embodiments the CD200 inhibitor and cancer vaccine may be in a combined formulation (i.e., a composition described herein) or may be in separate formulations for sequential or simultaneous administration.

As described herein, “enhancing efficacy” means a beneficial immune response is generated by the administration of a CD200 inhibitor and cancer vaccine that is greater than the beneficial immune response generated by the administration of just the cancer vaccine. In certain embodiments, administration of a CD200 inhibitor and a cancer vaccine (e.g., a composition described herein) reduces the size of a tumor (volume) in a mammal by 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% and this reduction is more than the reduction from administration the cancer vaccine alone.

The present invention also provides, in certain embodiments, a pharmaceutical composition which comprises a pharmaceutically acceptable carrier or diluent and, as an active ingredient, a conjugate or composition as described herein. In certain embodiments, the pharmaceutical composition is formulated for oral administration or injection.

The present invention also provides, in certain embodiments, a composition as described herein for use in a method of treatment of a human or animal body by therapy.

The present invention also provides, in certain embodiments, the use of a composition as described herein in the manufacture of a medicament for treating a disease or disorder arising from abnormal cell growth, function or behavior. In certain embodiments, the disease or disorder is cancer. In certain embodiments, the cancer is selected from solid tumors of the colon, breast, brain, liver, ovarian, gastric, lung, and head and neck. In certain embodiments, the cancer is selected from glioblastoma, melanoma, prostate, endometrial, ovarian, breast, lung, head and neck, hepatocellular, and thyroid cancers. In certain embodiments, the cancer is selected from breast, ovary, cervix, prostate, testis, genitourinary tract, esophagus, larynx, glioblastoma, neuroblastoma, stomach, skin, keratoacanthoma, lung, epidermoid carcinoma, large cell carcinoma, non-small cell lung carcinoma (NSCLC), small cell carcinoma, lung adenocarcinoma, bone, colon, adenoma, pancreas, adenocarcinoma, thyroid, follicular carcinoma, undifferentiated carcinoma, papillary carcinoma, seminoma, melanoma, sarcoma, bladder carcinoma, liver carcinoma and biliary passages, kidney carcinoma, myeloid disorders, lymphoid disorders, hairy cells, buccal cavity and pharynx (oral), lip, tongue, mouth, pharynx, small intestine, colon-rectum, large intestine, rectum, brain and central nervous system, Hodgkin's lymphoma and leukemia.

The present invention also provides, in certain embodiments, a method of treating a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition as described herein. In certain embodiments, the disease or disorder is cancer. In certain embodiments, the cancer is selected from glioblastoma, melanoma, prostate, endometrial, ovarian, breast, lung, head and neck, hepatocellular, and thyroid cancers. In certain embodiments, the cancer is selected from breast, ovary, cervix, prostate, testis, genitourinary tract, esophagus, larynx, glioblastoma, neuroblastoma, stomach, skin, keratoacanthoma, lung, epidermoid carcinoma, large cell carcinoma, non-small cell lung carcinoma (NSCLC), small cell carcinoma, lung adenocarcinoma, bone, colon, adenoma, pancreas, adenocarcinoma, thyroid, follicular carcinoma, undifferentiated carcinoma, papillary carcinoma, seminoma, melanoma, sarcoma, bladder carcinoma, liver carcinoma and biliary passages, kidney carcinoma, myeloid disorders, lymphoid disorders, hairy cells, buccal cavity and pharynx (oral), lip, tongue, mouth, pharynx, small intestine, colon-rectum, large intestine, rectum, brain and central nervous system, Hodgkin's lymphoma and leukemia.

Methods for Making Tumor Lysates

Tumor lysates are made by extracting a sample of the tumor to be treated from the subject. The tumor cells are then lysed. Methods of making effective tumor lysates include, but are not limited to, freeze thaw method, sonication, microwave, boiling, high heat, detergent or chemical-based cell lysis, electric or current-based lysis, and other physical methods, such as extreme force.

In certain embodiments, such as when a glioma is to be treated, EGF receptor VIII variant and IL-13 receptor alpha-2, which are glioma specific receptors (or expression vectors encoding these proteins), may be added to the tumor lysate.

Pharmaceutical Compositions

The present invention also provides, in certain embodiments, a process for producing a pharmaceutical composition comprising combining a composition as described herein with a pharmaceutically acceptable carrier.

The present invention also provides, in certain embodiments, a kit for treating cancer, comprising: (a) a first pharmaceutical composition comprising a composition as described herein; and (b) instructions for use.

Nucleic Acids, Expression Cassettes and Vectors

The present invention further provides nucleic acid sequences that encode the CD200 inhibitor peptides and adjuvants described above (e.g., in a fusion protein). The nucleic acids encoding the CD200 peptides and adjuvants can be produced using the methods well known in the art (see, e.g., Sambrook and Russell, 2001).

Accordingly, in certain embodiments of the invention provide a nucleic acid molecule encoding a CD200 inhibitor peptide and adjuvant as described herein.

Certain embodiments of the invention provide an expression cassette comprising a nucleic acid molecule described herein. In certain embodiments, the expression cassette described herein further comprises a promoter, such as a regulatable promoter or a constitutive promoter. Examples of suitable promoters include a CMV, RSV, pol II or pol III promoter. The expression cassette may further contain a polyadenylation signal (such as a synthetic minimal polyadenylation signal) and/or a marker gene.

Certain embodiments of the invention provide a viral vector comprising an expression cassette described herein. Examples of appropriate vectors include adenoviral, lentiviral, adeno-associated viral (AAV), poliovirus, HSV, or murine Maloney-based viral vectors. In certain embodiments, the vector is an adenovirus (Ad).

In certain embodiments, the viral vector is delivered directly into the tumor mass of a mammal. In certain embodiments, a cancer vaccine is administered to the mammal prior to delivery of the viral vector, simultaneously with the viral vector delivery or after delivery of the viral vector.

The present invention provides cells (such as a mammalian cell) containing the expression cassette or vectors described above. The present invention also provides a non-human mammal containing the expression cassette or vectors described above.

To immunize a subject, the composition is administered parenterally, usually by intramuscular or subcutaneous injection in an appropriate vehicle. Other modes of administration, however, such as oral, intranasal or intradermal delivery, are also acceptable.

Vaccine formulations will contain an effective amount of the active ingredient in a vehicle, the effective amount being readily determined by one skilled in the art. The active ingredient may typically range from about 1% to about 95% (w/w) of the composition, or even higher or lower if appropriate. The quantity to be administered depends upon factors such as the age, weight and physical condition of the animal or the human subject considered for vaccination. The quantity also depends upon the capacity of the animal's immune system to synthesize antibodies, and the degree of protection desired. Effective dosages can be readily established by one of ordinary skill in the art through routine trials establishing dose response curves. The subject is immunized by administration of the biofilm peptide or fragment thereof in one or more doses. Multiple doses may be administered as is required to maintain a state of immunity to the bacterium of interest.

Intranasal formulations may include vehicles that neither cause irritation to the nasal mucosa nor significantly disturb ciliary function. Diluents such as water, aqueous saline or other known substances can be employed with the subject invention. The nasal formulations may also contain preservatives such as, but not limited to, chlorobutanol and benzalkonium chloride. A surfactant may be present to enhance absorption of the subject proteins by the nasal mucosa.

Oral liquid preparations may be in the form of, for example, aqueous or oily suspension, solutions, emulsions, syrups or elixirs, or may be presented dry in tablet form or a product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous vehicles (which may include edible oils), or preservative.

To prepare a vaccine, the purified composition can be isolated, lyophilized and stabilized. The composition may then be adjusted to an appropriate concentration, optionally combined with a suitable vaccine adjuvant, and packaged for use.

DEFINITIONS

“Bound” refers to binding or attachment that may be covalent, e.g., by chemically coupling, or non-covalent, e.g., ionic interactions, hydrophobic interactions, hydrogen bonds. Covalent bonds can be, for example, ester, ether, phosphoester, amide, peptide, imide, carbon-sulfur bonds, carbon-phosphorus bonds, and the like. The term “bound” includes terms such as “linked,” “conjugated,” “coupled,” “fused” and “attached.”

The invention encompasses isolated or substantially purified protein (or peptide) compositions. In the context of the present invention, an “isolated” or “purified” polypeptide is a polypeptide that exists apart from its native environment and is therefore not a product of nature. A polypeptide may exist in a purified form or may exist in a non-native environment such as, for example, a transgenic host cell. For example, an “isolated” or “purified” protein, or biologically active portion thereof, is substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized. A protein that is substantially free of cellular material includes preparations of protein or polypeptide having less than about 30%, 20%, 10%, 5%, (by dry weight) of contaminating protein. When the protein of the invention, or biologically active portion thereof, is recombinantly produced, preferably culture medium represents less than about 30%, 20%, 10%, or 5% (by dry weight) of chemical precursors or non-protein-of-interest chemicals. Fragments and variants of the disclosed proteins or partial-length proteins encoded thereby are also encompassed by the present invention. By “fragment” or “portion” is meant a full length or less than full length of the amino acid sequence of, a polypeptide or protein.

“Naturally occurring” is used to describe an object that can be found in nature as distinct from being artificially produced. For example, a protein or nucleotide sequence present in an organism (including a virus), which can be isolated from a source in nature and which has not been intentionally modified by man in the laboratory, is naturally occurring.

A “variant” of a molecule is a sequence that is substantially similar to the sequence of the native molecule. For nucleotide sequences, variants include those sequences that, because of the degeneracy of the genetic code, encode the identical amino acid sequence of the native protein. Naturally occurring allelic variants such as these can be identified with the use of well-known molecular biology techniques, as, for example, with polymerase chain reaction (PCR) and hybridization techniques. Variant nucleotide sequences also include synthetically derived nucleotide sequences, such as those generated, for example, by using site-directed mutagenesis that encode the native protein, as well as those that encode a polypeptide having amino acid substitutions. Generally, nucleotide sequence variants of the invention will have in at least one embodiment 40%, 50%, 60%, to 70%, e.g., 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, to 79%, generally at least 80%, e.g., 81%-84%, at least 85%, e.g., 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, to 98%, sequence identity to the native (endogenous) nucleotide sequence.

“Wild-type” refers to the normal gene, or organism found in nature without any known mutation.

“Operably-linked” refers to the association of molecules so that the function of one is affected by the other. For example, operably-linked nucleic acids refers to the association of nucleic acid sequences on single nucleic acid fragment so that the function of one is affected by the other, e.g., an arrangement of elements wherein the components so described are configured so as to perform their usual function. For example, a regulatory DNA sequence is said to be “operably linked to” or “associated with” a DNA sequence that codes for an RNA or a polypeptide if the two sequences are situated such that the regulatory DNA sequence affects expression of the coding DNA sequence (i.e., that the coding sequence or functional RNA is under the transcriptional control of the promoter). Coding sequences can be operably-linked to regulatory sequences in sense or antisense orientation. Control elements operably linked to a coding sequence are capable of effecting the expression of the coding sequence. The control elements need not be contiguous with the coding sequence, so long as they function to direct the expression thereof. Thus, for example, intervening untranslated yet transcribed sequences can be present between a promoter and the coding sequence and the promoter can still be considered “operably linked” to the coding sequence.

“Operably-linked” also refers to the association of peptides, such that a linked peptide still functions as intended even when linked to another peptide. For example, if a CD200 inhibitor is operably linked to an adjuvant, the resulting linked protein still retains the function of inhibiting CD200 and also retains an immune-stimulating adjuvant function.

The term “substantial identity” in the context of a peptide indicates that a peptide comprises a sequence with at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, or 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, or 89%, at least 90%, 91%, 92%, 93%, or 94%, or 95%, 96%, 97%, 98% or 99%, sequence identity to a reference sequence over a specified comparison window. Optimal alignment is conducted using the homology alignment algorithm of Needleman and Wunsch, J. Mol. Biol. 48:443 (1970). An indication that two peptide sequences are substantially identical is that one peptide is immunologically reactive with antibodies raised against the second peptide. Thus, a peptide is substantially identical to a second peptide, for example, where the two peptides differ only by a conservative substitution.

For sequence comparison, typically one sequence acts as a reference sequence to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequence coordinates are designated if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters.

By “variant” polypeptide is intended a polypeptide derived from the native protein by deletion (so-called truncation) or addition of one or more amino acids to the N-terminal and/or C-terminal end of the native protein; deletion or addition of one or more amino acids at one or more sites in the native protein; or substitution of one or more amino acids at one or more sites in the native protein. Such variants may results form, for example, genetic polymorphism or from human manipulation. Methods for such manipulations are generally known in the art.

Thus, the polypeptides of the invention may be altered in various ways including amino acid substitutions, deletions, truncations, and insertions. Methods for such manipulations are generally known in the art. For example, amino acid sequence variants of the polypeptides can be prepared by mutations in the DNA. Methods for mutagenesis and nucleotide sequence alterations are well known in the art. See, for example, Kunkel, Proc. Natl. Acad. Sci. USA, 82:488 (1985); Kunkel et al., Meth. Enzymol., 154:367 (1987); U.S. Pat. No. 4,873,192; Walker and Gaastra, Techniques in Mol. Biol. (MacMillan Publishing Co. (1983), and the references cited therein. Guidance as to appropriate amino acid substitutions that do not affect biological activity of the protein of interest may be found in the model of Dayhoff et al., Atlas of Protein Sequence and Structure (Natl. Biomed. Res. Found. 1978). Conservative substitutions, such as exchanging one amino acid with another having similar properties, are preferred.

Thus, the polypeptides of the invention encompass naturally occurring proteins as well as variations and modified forms thereof. Such variants will continue to possess the desired activity. The deletions, insertions, and substitutions of the polypeptide sequence encompassed herein are not expected to produce radical changes in the characteristics of the polypeptide. However, when it is difficult to predict the exact effect of the substitution, deletion, or insertion in advance of doing so, one skilled in the art will appreciate that the effect will be evaluated by routine screening assays.

Individual substitutions deletions or additions that alter, add or delete a single amino acid or a small percentage of amino acids (typically less than 5%, more typically less than 1%) in an encoded sequence are “conservatively modified variations,” where the alterations result in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art. The following five groups each contain amino acids that are conservative substitutions for one another: Aliphatic: Glycine (G), Alanine (A), Valine (V), Leucine (L), Isoleucine (I); Aromatic: Phenylalanine (F), Tyrosine (Y), Tryptophan (W); Sulfur-containing: Methionine (M), Cysteine (C); Basic: Arginine (R), Lysine (K), Histidine (H); Acidic: Aspartic acid (D), Glutamic acid (E), Asparagine (N), Glutamine (Q). In addition, individual substitutions, deletions or additions which alter, add or delete a single amino acid or a small percentage of amino acids in an encoded sequence are also “conservatively modified variations.”

As used herein, the term “nucleic acid” and “polynucleotide” refers to deoxyribonucleotides or ribonucleotides and polymers thereof in either single- or double-stranded form, composed of monomers (nucleotides) containing a sugar, phosphate and a base that is either a purine or pyrimidine. Unless specifically limited, the term encompasses nucleic acids containing known analogs of natural nucleotides which have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions) and complementary sequences as well as the sequence explicitly indicated. Specifically, degenerate codon substitutions may be achieved by generating sequences in which the third position of one or more selected (or all) codons is substituted with mixed-base and/or deoxyinosine residues.

A “nucleic acid fragment” is a portion of a given nucleic acid molecule. Deoxyribonucleic acid (DNA) in the majority of organisms is the genetic material while ribonucleic acid (RNA) is involved in the transfer of information contained within DNA into proteins. The term “nucleotide sequence” refers to a polymer of DNA or RNA which can be single- or double-stranded, optionally containing synthetic, non-natural or altered nucleotide bases capable of incorporation into DNA or RNA polymers.

The terms “nucleic acid,” “nucleic acid molecule,” “nucleic acid fragment,” “nucleic acid sequence or segment,” or “polynucleotide” may also be used interchangeably with gene, cDNA, DNA and RNA encoded by a gene, e.g., genomic DNA, and even synthetic DNA sequences. The term also includes sequences that include any of the known base analogs of DNA and RNA.

The term “gene” is used broadly to refer to any segment of nucleic acid associated with a biological function. Genes include coding sequences and/or the regulatory sequences required for their expression. For example, gene refers to a nucleic acid fragment that expresses mRNA, functional RNA, or a specific protein, including its regulatory sequences. Genes also include nonexpressed DNA segments that, for example, form recognition sequences for other proteins. Genes can be obtained from a variety of sources, including cloning from a source of interest or synthesizing from known or predicted sequence information, and may include sequences designed to have desired parameters. In addition, a “gene” or a “recombinant gene” refers to a nucleic acid molecule comprising an open reading frame and including at least one exon and (optionally) an intron sequence. The term “intron” refers to a DNA sequence present in a given gene which is not translated into protein and is generally found between exons.

A “vector” is defined to include, inter alia, any viral vector, as well as any plasmid, cosmid, phage or binary vector in double or single stranded linear or circular form that may or may not be self transmissible or mobilizable, and that can transform prokaryotic or eukaryotic host either by integration into the cellular genome or exist extrachromosomally (e.g., autonomous replicating plasmid with an origin of replication).

The term “transformation” refers to the transfer of a nucleic acid fragment into the genome of a host cell, resulting in genetically stable inheritance. A “host cell” is a cell that has been transformed, or is capable of transformation, by an exogenous nucleic acid molecule. Host cells containing the transformed nucleic acid fragments are referred to as “transgenic” cells.

“Transformed,” “transduced,” “transgenic” and “recombinant” refer to a host cell into which a heterologous nucleic acid molecule has been introduced. As used herein the term “transfection” refers to the delivery of DNA into eukaryotic (e.g., mammalian) cells. The term “transformation” is used herein to refer to delivery of DNA into prokaryotic (e.g., E. coli) cells. The term “transduction” is used herein to refer to infecting cells with viral particles. The nucleic acid molecule can be stably integrated into the genome generally known in the art. Known methods of PCR include, but are not limited to, methods using paired primers, nested primers, single specific primers, degenerate primers, gene-specific primers, vector-specific primers, partially mismatched primers, and the like. For example, “transformed,” “transformant,” and “transgenic” cells have been through the transformation process and contain a foreign gene integrated into their chromosome. The term “untransformed” refers to normal cells that have not been through the transformation process.

“Genetically altered cells” denotes cells which have been modified by the introduction of recombinant or heterologous nucleic acids (e.g., one or more DNA constructs or their RNA counterparts) and further includes the progeny of such cells which retain part or all of such genetic modification.

As used herein, the term “derived” or “directed to” with respect to a nucleotide molecule means that the molecule has complementary sequence identity to a particular molecule of interest.

“Expression cassette” as used herein means a nucleic acid sequence capable of directing expression of a particular nucleotide sequence in an appropriate host cell, which may include a promoter operably linked to the nucleotide sequence of interest that may be operably linked to termination signals. The coding region usually codes for a functional peptide of interest, for example a CD200 inhibitor. The expression cassette including the nucleotide sequence of interest may be chimeric. The expression cassette may also be one that is naturally occurring but has been obtained in a recombinant form useful for heterologous expression. The expression of the nucleotide sequence in the expression cassette may be under the control of a constitutive promoter or of an regulatable promoter that initiates transcription only when the host cell is exposed to some particular stimulus. In the case of a multicellular organism, the promoter can also be specific to a particular tissue or organ or stage of development.

Such expression cassettes can include a transcriptional initiation region linked to a nucleotide sequence of interest. Such an expression cassette is provided with a plurality of restriction sites for insertion of the gene of interest to be under the transcriptional regulation of the regulatory regions. The expression cassette may additionally contain selectable marker genes.

The term “RNA transcript” or “transcript” refers to the product resulting from RNA polymerase catalyzed transcription of a DNA sequence. When the RNA transcript is a perfect complementary copy of the DNA sequence, it is referred to as the primary transcript or it may be a RNA sequence derived from posttranscriptional processing of the primary transcript and is referred to as the mature RNA. “Messenger RNA” (mRNA) refers to the RNA that is without introns and that can be translated into protein by the cell. “cDNA” refers to a single- or a double-stranded DNA that is complementary to and derived from mRNA.

“Regulatory sequences” are nucleotide sequences located upstream (5′ non-coding sequences), within, or downstream (3′ non-coding sequences) of a coding sequence, and which influence the transcription, RNA processing or stability, or translation of the associated coding sequence. Regulatory sequences include enhancers, promoters, translation leader sequences, introns, and polyadenylation signal sequences. They include natural and synthetic sequences as well as sequences that may be a combination of synthetic and natural sequences. As is noted above, the term “suitable regulatory sequences” is not limited to promoters. However, some suitable regulatory sequences useful in the present invention will include, but are not limited to constitutive promoters, tissue-specific promoters, development-specific promoters, regulatable promoters and viral promoters.

“5′ non-coding sequence” refers to a nucleotide sequence located 5′ (upstream) to the coding sequence. It is present in the fully processed mRNA upstream of the initiation codon and may affect processing of the primary transcript to mRNA, mRNA stability or translation efficiency (Turner et al., 1995).

“3′ non-coding sequence” refers to nucleotide sequences located 3′ (downstream) to a coding sequence and may include polyadenylation signal sequences and other sequences encoding regulatory signals capable of affecting mRNA processing or gene expression. The polyadenylation signal is usually characterized by affecting the addition of polyadenylic acid tracts to the 3′ end of the mRNA precursor.

“Promoter” refers to a nucleotide sequence, usually upstream (5′) to its coding sequence, which directs and/or controls the expression of the coding sequence by providing the recognition for RNA polymerase and other factors required for proper transcription. “Promoter” includes a minimal promoter that is a short DNA sequence comprised of a TATA-box and other sequences that serve to specify the site of transcription initiation, to which regulatory elements are added for control of expression. “Promoter” also refers to a nucleotide sequence that includes a minimal promoter plus regulatory elements that is capable of controlling the expression of a coding sequence or functional RNA. This type of promoter sequence consists of proximal and more distal upstream elements, the latter elements often referred to as enhancers. Accordingly, an “enhancer” is a DNA sequence that can stimulate promoter activity and may be an innate element of the promoter or a heterologous element inserted to enhance the level or tissue specificity of a promoter. It is capable of operating in both orientations (normal or flipped), and is capable of functioning even when moved either upstream or downstream from the promoter. Both enhancers and other upstream promoter elements bind sequence-specific DNA-binding proteins that mediate their effects. Promoters may be derived in their entirety from a native gene, or be composed of different elements derived from different promoters found in nature, or even be comprised of synthetic DNA segments. A promoter may also contain DNA sequences that are involved in the binding of protein factors that control the effectiveness of transcription initiation in response to physiological or developmental conditions. Examples of promoters that may be used in the present invention include the mouse U6 RNA promoters, synthetic human H1RNA promoters, SV40, CMV, RSV, RNA polymerase II and RNA polymerase III promoters.

“Constitutive expression” refers to expression using a constitutive or regulated promoter. “Conditional” and “regulated expression” refer to expression controlled by a regulated promoter.

“Expression” refers to the transcription and/or translation of an endogenous gene, heterologous gene or nucleic acid segment, or a transgene in cells. Expression may also refer to the production of protein.

“Homology” refers to the percent identity between two polynucleotides or two polypeptide sequences. Two DNA or polypeptide sequences are “homologous” to each other when the sequences exhibit at least about 75% to 85% (including 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, and 85%), at least about 90%, or at least about 95% to 99% (including 95%, 96%, 97%, 98%, 99%) contiguous sequence identity over a defined length of the sequences.

The following terms are used to describe the sequence relationships between two or more nucleic acids or polynucleotides: (a) “reference sequence,” (b) “comparison window,” (c) “sequence identity,” (d) “percentage of sequence identity,” and (e) “substantial identity.”

(a) As used herein, “reference sequence” is a defined sequence used as a basis for sequence comparison. A reference sequence may be a subset or the entirety of a specified sequence; for example, as a segment of a full length cDNA or gene sequence, or the complete cDNA or gene sequence.

(b) As used herein, “comparison window” makes reference to a contiguous and specified segment of a polynucleotide sequence, wherein the polynucleotide sequence in the comparison window may comprise additions or deletions (i.e., gaps) compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. Generally, the comparison window is at least 20 contiguous nucleotides in length, and optionally can be 30, 40, 50, 100, or longer. Those of skill in the art understand that to avoid a high similarity to a reference sequence due to inclusion of gaps in the polynucleotide sequence a gap penalty is typically introduced and is subtracted from the number of matches.

Methods of alignment of sequences for comparison are well known in the art. Thus, the determination of percent identity between any two sequences can be accomplished using a mathematical algorithm.

Computer implementations of these mathematical algorithms can be utilized for comparison of sequences to determine sequence identity. Such implementations include, but are not limited to: CLUSTAL in the PC/Gene program (available from Intelligenetics, Mountain View, Calif.); the ALIGN program (Version 2.0) and GAP, BESTFIT, BLAST, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Version 8 (available from Genetics Computer Group (GCG), 575 Science Drive, Madison, Wis., USA). Alignments using these programs can be performed using the default parameters.

Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (see the World Wide Web at ncbi.nlm.nih.gov). This algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold. These initial neighborhood word hits act as seeds for initiating searches to find longer HSPs containing them. The word hits are then extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when the cumulative alignment score falls off by the quantity X from its maximum achieved value, the cumulative score goes to zero or below due to the accumulation of one or more negative-scoring residue alignments, or the end of either sequence is reached.

In addition to calculating percent sequence identity, the BLAST algorithm also performs a statistical analysis of the similarity between two sequences. One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a test nucleic acid sequence is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid sequence to the reference nucleic acid sequence is less than about 0.1, less than about 0.01, or even less than about 0.001.

To obtain gapped alignments for comparison purposes, Gapped BLAST (in BLAST 2.0) can be utilized. Alternatively, PSI-BLAST (in BLAST 2.0) can be used to perform an iterated search that detects distant relationships between molecules. When using BLAST, Gapped BLAST, PSI-BLAST, the default parameters of the respective programs (e.g., BLASTN for nucleotide sequences, BLASTX for proteins) can be used. The BLASTN program (for nucleotide sequences) uses as defaults a wordlength (W) of 11, an expectation (E) of 10, a cutoff of 100, M=5, N=−4, and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a wordlength (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix. See the World Wide Web at ncbi.nlm.nih.gov. Alignment may also be performed manually by visual inspection.

For purposes of the present invention, comparison of nucleotide sequences for determination of percent sequence identity to the sequences disclosed herein is preferably made using the BlastN program (version 1.4.7 or later) with its default parameters or any equivalent program. By “equivalent program” is intended any sequence comparison program that, for any two sequences in question, generates an alignment having identical nucleotide or amino acid residue matches and an identical percent sequence identity when compared to the corresponding alignment generated by a BLAST program.

(c) As used herein, “sequence identity” or “identity” in the context of two nucleic acid sequences makes reference to a specified percentage of residues in the two sequences that are the same when aligned for maximum correspondence over a specified comparison window, as measured by sequence comparison algorithms or by visual inspection. When percentage of sequence identity is used in reference to proteins, it is recognized that residue positions that are not identical often differ by conservative amino acid substitutions, where amino acid residues are substituted for other amino acid residues with similar chemical properties (e.g., charge or hydrophobicity) and therefore do not change the functional properties of the molecule. When sequences differ in conservative substitutions, the percent sequence identity may be adjusted upwards to correct for the conservative nature of the substitution. Sequences that differ by such conservative substitutions are said to have “sequence similarity” or “similarity.” Means for making this adjustment are well known to those of skill in the art. Typically this involves scoring a conservative substitution as a partial rather than a full mismatch, thereby increasing the percentage sequence identity. Thus, for example, where an identical amino acid is given a score of 1 and a non-conservative substitution is given a score of zero, a conservative substitution is given a score between zero and 1. The scoring of conservative substitutions is calculated, e.g., as implemented in the program PC/GENE (Intelligenetics, Mountain View, Calif.).

(d) As used herein, “percentage of sequence identity” means the value determined by comparing two optimally aligned sequences over a comparison window, wherein the portion of the polynucleotide sequence in the comparison window may comprise additions or deletions (i.e., gaps) as compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. The percentage is calculated by determining the number of positions at which the identical nucleic acid base occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison, and multiplying the result by 100 to yield the percentage of sequence identity.

(e)(i) The term “substantial identity” of polynucleotide sequences means that a polynucleotide comprises a sequence that has at least 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, or 79%; at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, or 89%; at least 90%, 91%, 92%, 93%, or 94%; or even at least 95%, 96%, 97%, 98%, or 99% sequence identity, compared to a reference sequence using one of the alignment programs described using standard parameters.

Another indication that nucleotide sequences are substantially identical is if two molecules hybridize to each other under stringent conditions (see below). Generally, stringent conditions are selected to be about 5° C. lower than the thermal melting point (T_(m)) for the specific sequence at a defined ionic strength and pH. However, stringent conditions encompass temperatures in the range of about 1° C. to about 20° C., depending upon the desired degree of stringency as otherwise qualified herein. Nucleic acids that do not hybridize to each other under stringent conditions are still substantially identical if the polypeptides they encode are substantially identical. This may occur, e.g., when a copy of a nucleic acid is created using the maximum codon degeneracy permitted by the genetic code.

(e)(ii) For sequence comparison, typically one sequence acts as a reference sequence to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are input into a computer, subsequence coordinates are designated if necessary, and sequence algorithm program parameters are designated. The sequence comparison algorithm then calculates the percent sequence identity for the test sequence(s) relative to the reference sequence, based on the designated program parameters.

As noted above, another indication that two nucleic acid sequences are substantially identical is that the two molecules hybridize to each other under stringent conditions. The phrase “hybridizing specifically to” refers to the binding, duplexing, or hybridizing of a molecule only to a particular nucleotide sequence under stringent conditions when that sequence is present in a complex mixture (e.g., total cellular) DNA or RNA. “Bind(s) substantially” refers to complementary hybridization between a probe nucleic acid and a target nucleic acid and embraces minor mismatches that can be accommodated by reducing the stringency of the hybridization media to achieve the desired detection of the target nucleic acid sequence.

“Stringent hybridization conditions” and “stringent hybridization wash conditions” in the context of nucleic acid hybridization experiments such as Southern and Northern hybridizations are sequence dependent, and are different under different environmental parameters. Longer sequences hybridize specifically at higher temperatures. The T_(m) is the temperature (under defined ionic strength and pH) at which 50% of the target sequence hybridizes to a perfectly matched nucleic acid. Specificity is typically the function of post-hybridization washes, the critical factors being the ionic strength and temperature of the final wash solution. For DNA-DNA hybrids, the T_(m) can be approximated from the equation of Meinkoth and Wahl:

T _(m) 81.5° C.+16.6(log M)+0.41(% GC)−0.61(% form)−500/L

where M is the molarity of monovalent cations, % GC is the percentage of guanosine and cytosine nucleotides in the DNA, % form is the percentage of formamide in the hybridization solution, and L is the length of the hybrid in base pairs. T_(m) is reduced by about 1° C. for each 1% of mismatching; thus, T_(m), hybridization, and/or wash conditions can be adjusted to hybridize to sequences of the desired identity. For example, if sequences with >90% identity are sought, the T_(m) can be decreased 10° C. Generally, stringent conditions are selected to be about 5° C. lower than the thermal melting point (T_(m)) for the specific sequence and its complement at a defined ionic strength and pH. However, severely stringent conditions can utilize a hybridization and/or wash at 1, 2, 3, or 4° C. lower than the thermal melting point (T_(m)); moderately stringent conditions can utilize a hybridization and/or wash at 6, 7, 8, 9, or 10° C. lower than the thermal melting point (T_(m)); low stringency conditions can utilize a hybridization and/or wash at 11, 12, 13, 14, 15, or 20° C. lower than the thermal melting point (T_(m)). Using the equation, hybridization and wash compositions, and desired T, those of ordinary skill will understand that variations in the stringency of hybridization and/or wash solutions are inherently described. If the desired degree of mismatching results in a T of less than 45° C. (aqueous solution) or 32° C. (formamide solution), it is preferred to increase the SSC concentration so that a higher temperature can be used. Generally, highly stringent hybridization and wash conditions are selected to be about 5° C. lower than the thermal melting point (T_(m)) for the specific sequence at a defined ionic strength and pH.

An example of highly stringent wash conditions is 0.15 M NaCl at 72° C. for about 15 minutes. An example of stringent wash conditions is a 0.2×SSC wash at 65° C. for 15 minutes. Often, a high stringency wash is preceded by a low stringency wash to remove background probe signal. An example medium stringency wash for a duplex of, e.g., more than 100 nucleotides, is 1×SSC at 45° C. for 15 minutes. An example low stringency wash for a duplex of, e.g., more than 100 nucleotides, is 4-6×SSC at 40° C. for 15 minutes. For short probes (e.g., about 10 to 50 nucleotides), stringent conditions typically involve salt concentrations of less than about 1.5 M, more preferably about 0.01 to 1.0 M, Na ion concentration (or other salts) at pH 7.0 to 8.3, and the temperature is typically at least about 30° C. and at least about 60° C. for long probes (e.g., >50 nucleotides). Stringent conditions may also be achieved with the addition of destabilizing agents such as formamide. In general, a signal to noise ratio of 2× (or higher) than that observed for an unrelated probe in the particular hybridization assay indicates detection of a specific hybridization.

Very stringent conditions are selected to be equal to the T_(m) for a particular probe. An example of stringent conditions for hybridization of complementary nucleic acids which have more than 100 complementary residues on a filter in a Southern or Northern blot is 50% formamide, e.g., hybridization in 50% formamide, 1 M NaCl, 1% SDS at 37° C., and a wash in 0.1×SSC at 60 to 65° C. Exemplary low stringency conditions include hybridization with a buffer solution of 30 to 35% formamide, 1M NaCl, 1% SDS (sodium dodecyl sulphate) at 37° C., and a wash in 1× to 2×SSC (20×SSC=3.0 M NaCl/0.3 M trisodium citrate) at 50 to 55° C. Exemplary moderate stringency conditions include hybridization in 40 to 45% formamide, 1.0 M NaCl, 1% SDS at 37° C., and a wash in 0.5× to 1×SSC at 55 to 60° C.

As discussed above, the terms “isolated and/or purified” in terms of a nucleic acid refer to in vitro isolation of a nucleic acid, e.g., a DNA or RNA molecule from its natural cellular environment, and from association with other components of the cell, such as nucleic acid or polypeptide, so that it can be sequenced, replicated, and/or expressed. For example, “isolated nucleic acid” may be a DNA molecule that is complementary or hybridizes to a sequence in a gene of interest and remains stably bound under stringent conditions (as defined by methods well known in the art). Thus, the RNA or DNA is “isolated” in that it is free from at least one contaminating nucleic acid with which it is normally associated in the natural source of the RNA or DNA and in one embodiment of the invention is substantially free of any other mammalian RNA or DNA. The phrase “free from at least one contaminating source nucleic acid with which it is normally associated” includes the case where the nucleic acid is reintroduced into the source or natural cell but is in a different chromosomal location or is otherwise flanked by nucleic acid sequences not normally found in the source cell, e.g., in a vector or plasmid.

As used herein, the term “recombinant nucleic acid,” e.g., “recombinant DNA sequence or segment” refers to a nucleic acid, e.g., to DNA, that has been derived or isolated from any appropriate cellular source, that may be subsequently chemically altered in vitro, so that its sequence is not naturally occurring, or corresponds to naturally occurring sequences that are not positioned as they would be positioned in a genome that has not been transformed with exogenous DNA. An example of preselected DNA “derived” from a source would be a DNA sequence that is identified as a useful fragment within a given organism, and which is then chemically synthesized in essentially pure form. An example of such DNA “isolated” from a source would be a useful DNA sequence that is excised or removed from said source by chemical means, e.g., by the use of restriction endonucleases, so that it can be further manipulated, e.g., amplified, for use in the invention, by the methodology of genetic engineering.

Thus, recovery or isolation of a given fragment of DNA from a restriction digest can employ separation of the digest on polyacrylamide or agarose gel by electrophoresis, identification of the fragment of interest by comparison of its mobility versus that of marker DNA fragments of known molecular weight, removal of the gel section containing the desired fragment, and separation of the gel from DNA. Therefore, “recombinant DNA” includes completely synthetic DNA sequences, semi-synthetic DNA sequences, DNA sequences isolated from biological sources, and DNA sequences derived from RNA, as well as mixtures thereof

Nucleic acid molecules having base substitutions (i.e., variants) are prepared by a variety of methods known in the art. These methods include, but are not limited to, isolation from a natural source (in the case of naturally occurring sequence variants) or preparation by oligonucleotide-mediated (or site-directed) mutagenesis, PCR mutagenesis, and cassette mutagenesis of an earlier prepared variant or a non-variant version of the nucleic acid molecule.

As used herein, the term “therapeutic agent” or “therapeutic complex” refers to any agent or material that has a beneficial effect on the mammalian recipient. Thus, “therapeutic agent” embraces both therapeutic and prophylactic molecules having nucleic acid or protein components.

“Treating” as used herein refers to ameliorating at least one symptom of, curing and/or preventing the development of a given disease or condition.

An “immune response” refers to a humoral immune response and/or cellular immune response leading to the activation or proliferation of B- and/or T-lymphocytes and/or and antigen presenting cells. In some instances, however, the immune responses may be of low intensity and become detectable only when using at least one substance in accordance with the invention. “Immunogenic” refers to an agent used to stimulate the immune system of a living organism, so that one or more functions of the immune system are increased and directed towards the immunogenic agent. An “immunogenic polypeptide” is a polypeptide that elicits a cellular and/or humoral immune response, whether alone or linked to a carrier. Preferably, antigen presenting cell may be activated.

A substance that “enhances” an immune response refers to a substance in which an immune response is observed that is greater or intensified or deviated in any way with the addition of the substance when compared to the same immune response measured without the addition of the substance. For example, the lytic activity of cytotoxic T cells can be measured, e.g. using a ⁵¹Cr release assay, in samples obtained with and without the use of the substance during immunization. The amount of the substance at which the CTL lytic activity is enhanced as compared to the CTL lytic activity without the substance is said to be an amount sufficient to enhance the immune response of the animal to the antigen. In certain embodiments, the immune response in enhanced by a factor of at least about 2, such as by a factor of about 3 or more. The amount or type of cytokines secreted may also be altered. Alternatively, the amount of antibodies induced or their subclasses may be altered.

The terms “immunize” or “immunization” or related terms refer to conferring the ability to mount a substantial immune response (comprising antibodies and/or cellular immunity such as effector CTL) against a target antigen or epitope. These terms do not require that complete immunity be created, but rather that an immune response be produced which is substantially greater than baseline. For example, a mammal may be considered to be immunized against a target antigen if the cellular and/or humoral immune response to the target antigen occurs following the application of methods of the invention.

The term “immunotherapeutic” refers to a composition for the treatment of diseases, disorders or conditions. More specifically, the term is used to refer to a method of treatment wherein a beneficial immune response is generated by vaccination or by transfer of immune molecules. An “immunologically effective amount” refers to an amount of a composition sufficient to induce an immune response in an individual when introduced into that individual. In the context of active immunization, the term is synonymous with “immunogenically effective amount.” The amount of a composition necessary to be immunologically effective varies according many factors including to the composition, the presence of other components in the composition, the antigen, the route of immunization, the individual, the prior immune or physiologic state etc.

Formulations and Methods of Administration

The vaccines and compositions of the invention may be formulated as pharmaceutical compositions and administered to a mammalian host, such as a human patient, in a variety of forms adapted to the chosen route of administration, i.e., orally, intranasally, intradermally or parenterally, by intravenous, intramuscular, topical or subcutaneous routes.

Thus, the present compounds may be systemically administered, e.g., orally, in combination with a pharmaceutically acceptable vehicle such as an inert diluent or an assimilable edible carrier. They may be enclosed in hard or soft shell gelatin capsules, may be compressed into tablets, or may be incorporated directly with the food of the patient's diet. For oral therapeutic administration, the active compound may be combined with one or more excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of active compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of a given unit dosage form. The amount of active compound in such therapeutically useful compositions is such that an effective dosage level will be obtained.

The tablets, troches, pills, capsules, and the like may also contain the following: binders such as gum tragacanth, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, fructose, lactose or aspartame or a flavoring agent such as peppermint, oil of wintergreen, or cherry flavoring may be added. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like. A syrup or elixir may contain the active compound, sucrose or fructose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring such as cherry or orange flavor. Of course, any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non-toxic in the amounts employed. In addition, the active compound may be incorporated into sustained-release preparations and devices.

The active compound may also be administered intravenously or intraperitoneally by infusion or injection. Solutions of the active compound or its salts may be prepared in water, optionally mixed with a nontoxic surfactant. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, triacetin, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms.

The pharmaceutical dosage forms suitable for injection or infusion can include sterile aqueous solutions or dispersions or sterile powders comprising the active ingredient that are adapted for the extemporaneous preparation of sterile injectable or infusible solutions or dispersions, optionally encapsulated in liposomes. In all cases, the ultimate dosage form should be sterile, fluid and stable under the conditions of manufacture and storage. The liquid carrier or vehicle can be a solvent or liquid dispersion medium comprising, for example, water, ethanol, a polyol (for example, glycerol, propylene glycol, liquid polyethylene glycols, and the like), vegetable oils, nontoxic glyceryl esters, and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the formation of liposomes, by the maintenance of the required particle size in the case of dispersions or by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, buffers or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.

Sterile injectable solutions are prepared by incorporating the active compound in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filter sterilization. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze drying techniques, which yield a powder of the active ingredient plus any additional desired ingredient present in the previously sterile-filtered solutions. For topical administration, the present compounds may be applied in pure form, i.e., when they are liquids. However, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid.

Useful solid carriers include finely divided solids such as talc, clay, microcrystalline cellulose, silica, alumina and the like. Useful liquid carriers include water, alcohols or glycols or water-alcohol/glycol blends, in which the present compounds can be dissolved or dispersed at effective levels, optionally with the aid of non-toxic surfactants. Additional ingredients such as fragrances or antimicrobial agents can be added to optimize the properties for a given use. The resultant liquid compositions can be applied from absorbent pads, used to impregnate bandages and other dressings, or sprayed onto the affected area using pump-type or aerosol sprayers.

Thickeners such as synthetic polymers, fatty acids, fatty acid salts and esters, fatty alcohols, modified celluloses or modified mineral materials can also be employed with liquid carriers to form spreadable pastes, gels, ointments, soaps, and the like, for application directly to the skin of the user.

Examples of useful dermatological compositions that can be used to deliver the compounds of the present invention to the skin are known to the art; for example, see Jacquet et al. (U.S. Pat. No. 4,608,392), Geria (U.S. Pat. No. 4,992,478), Smith et al. (U.S. Pat. No. 4,559,157) and Wortzman (U.S. Pat. No. 4,820,508).

Useful dosages of the compounds of the present invention can be determined by comparing their in vitro activity, and in vivo activity in animal models. Methods for the extrapolation of effective dosages in mice, and other animals, to humans are known to the art; for example, see U.S. Pat. No. 4,938,949.

Generally, the concentration of the compound(s) of the present invention in a liquid composition, such as a lotion, will be from about 0.1-25 wt-%, preferably from about 0.5-10 wt-%. The concentration in a semi-solid or solid composition such as a gel or a powder will be about 0.1-5 wt-%, preferably about 0.5-2.5 wt-%.

The amount of the compound, or an active salt or derivative thereof, required for use in treatment will vary not only with the particular salt selected but also with the route of administration, the nature of the condition being treated and the age and condition of the patient and will be ultimately at the discretion of the attendant physician or clinician.

In general, however, a suitable dose will be in the range of from about 0.5 to about 100 mg/kg, e.g., from about 10 to about 75 mg/kg of body weight per day, such as 3 to about 50 mg per kilogram body weight of the recipient per day, preferably in the range of 6 to 90 mg/kg/day, most preferably in the range of 15 to 60 mg/kg/day.

The compound is conveniently administered in unit dosage form; for example, containing 5 to 1000 mg, conveniently 10 to 750 mg, most conveniently, 50 to 500 mg of active ingredient per unit dosage form.

Ideally, the active ingredient should be administered to achieve peak plasma concentrations of the active compound of from about 0.5 to about 75 preferably, about 1 to 50 μM, most preferably, about 2 to about 30 μM. This may be achieved, for example, by the intravenous injection of a 0.05 to 5% solution of the active ingredient, optionally in saline, or orally administered as a bolus containing about 1-100 mg of the active ingredient. Desirable blood levels may be maintained by continuous infusion to provide about 0.01-5.0 mg/kg/hr or by intermittent infusions containing about 0.4-15 mg/kg of the active ingredient(s).

The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example, as two, three, four or more sub-doses per day. The sub-dose itself may be further divided, e.g., into a number of discrete loosely spaced administrations; such as multiple inhalations from an insufflator or by application of a plurality of drops into the eye.

In certain embodiments, the vaccine of the present invention reduces the size of the tumor in the subject by at least about 10%-100% (volume of tumor).

Nucleic Acid Molecules of the Invention

The terms “isolated and/or purified” refer to in vitro isolation of a nucleic acid, e.g., a DNA or RNA molecule from its natural cellular environment, and from association with other components of the cell, such as nucleic acid or polypeptide, so that it can be sequenced, replicated, and/or expressed. For example, “isolated nucleic acid” may be a DNA molecule containing less than 100, 90, 80, 70, 60, 50, 40 or 20 sequential nucleotides that is transcribed and translated into a peptide. Such a peptide may be a competitive inhibitor to CD200 and bind to CD200R. Thus, the RNA or DNA is “isolated” in that it is free from at least one contaminating nucleic acid with which it is normally associated in the natural source of the RNA or DNA and is preferably substantially free of any other mammalian RNA or DNA. The phrase “free from at least one contaminating source nucleic acid with which it is normally associated” includes the case where the nucleic acid is reintroduced into the source or natural cell but is in a different chromosomal location or is otherwise flanked by nucleic acid sequences not normally found in the source cell, e.g., in a vector or plasmid.

As used herein, the term “recombinant nucleic acid”, e.g., “recombinant DNA sequence or segment” refers to a nucleic acid, e.g., to DNA, that has been derived or isolated from any appropriate cellular source, that may be subsequently chemically altered in vitro, so that its sequence is not naturally occurring, or corresponds to naturally occurring sequences that are not positioned as they would be positioned in a genome which has not been transformed with exogenous DNA. An example of preselected DNA “derived” from a source, would be a DNA sequence that is identified as a useful fragment within a given organism, and which is then chemically synthesized in essentially pure form. An example of such DNA “isolated” from a source would be a useful DNA sequence that is excised or removed from said source by chemical means, e.g., by the use of restriction endonucleases, so that it can be further manipulated, e.g., amplified, for use in the invention, by the methodology of genetic engineering.

Thus, recovery or isolation of a given fragment of DNA from a restriction digest can employ separation of the digest on polyacrylamide or agarose gel by electrophoresis, identification of the fragment of interest by comparison of its mobility versus that of marker DNA fragments of known molecular weight, removal of the gel section containing the desired fragment, and separation of the gel from DNA. Therefore, “recombinant DNA” includes completely synthetic DNA sequences, semi-synthetic DNA sequences, DNA sequences isolated from biological sources, and DNA sequences derived from RNA, as well as mixtures thereof.

Nucleic acid molecules having base substitutions (i.e., variants) are prepared by a variety of methods known in the art. These methods include, but are not limited to, isolation from a natural source (in the case of naturally occurring sequence variants) or preparation by oligonucleotide-mediated (or site-directed) mutagenesis, PCR mutagenesis, and cassette mutagenesis of an earlier prepared variant or a non-variant version of the nucleic acid molecule.

Oligonucleotide-mediated mutagenesis is a method for preparing substitution variants. This technique is known in the art as described by Adelman et al. (1983). Briefly, a nucleic acid encoding a peptide described herein can be altered by hybridizing an oligonucleotide encoding the desired mutation to a DNA template, where the template is the single-stranded form of a plasmid or bacteriophage containing the unaltered or native gene sequence. After hybridization, a DNA polymerase is used to synthesize an entire second complementary strand of the template that will thus incorporate the oligonucleotide primer, and will code for the selected alteration in the nucleic acid encoding the peptide. Generally, oligonucleotides of at least 25 nucleotides in length are used. An optimal oligonucleotide will have 12 to 15 nucleotides that are completely complementary to the template on either side of the nucleotide(s) coding for the mutation. This ensures that the oligonucleotide will hybridize properly to the single-stranded DNA template molecule. The oligonucleotides are readily synthesized using techniques known in the art.

The DNA template can be generated by those vectors that are either derived from bacteriophage M13 vectors (the commercially available M13mp18 and M13mp19 vectors are suitable), or those vectors that contain a single-stranded phage origin of replication. Thus, the DNA that is to be mutated may be inserted into one of these vectors to generate single-stranded template. Production of the single-stranded template is described in Chapter 3 of Sambrook and Russell, 2001. Alternatively, single-stranded DNA template may be generated by denaturing double-stranded plasmid (or other) DNA using standard techniques.

For alteration of the native DNA sequence (to generate amino acid sequence variants, for example), the oligonucleotide is hybridized to the single-stranded template under suitable hybridization conditions. A DNA polymerizing enzyme, usually the Klenow fragment of DNA polymerase I, is then added to synthesize the complementary strand of the template using the oligonucleotide as a primer for synthesis. A heteroduplex molecule is thus formed such that one strand of DNA encodes the mutated form of the DNA, and the other strand (the original template) encodes the native, unaltered sequence of the DNA. This heteroduplex molecule is then transformed into a suitable host cell, usually a prokaryote such as E. coli JM101. After the cells are grown, they are plated onto agarose plates and screened using the oligonucleotide primer radiolabeled with 32-phosphate to identify the bacterial colonies that contain the mutated DNA. The mutated region is then removed and placed in an appropriate vector, generally an expression vector of the type typically employed for transformation of an appropriate host.

The method described immediately above may be modified such that a homoduplex molecule is created wherein both strands of the plasmid contain the mutations(s). The modifications are as follows: The single-stranded oligonucleotide is annealed to the single-stranded template as described above. A mixture of three deoxyribonucleotides, deoxyriboadenosine (dATP), deoxyriboguanosine (dGTP), and deoxyribothymidine (dTTP), is combined with a modified thiodeoxyribocytosine called dCTP-(*S) (which can be obtained from the Amersham Corporation). This mixture is added to the template-oligonucleotide complex. Upon addition of DNA polymerase to this mixture, a strand of DNA identical to the template except for the mutated bases is generated. In addition, this new strand of DNA will contain dCTP-(*S) instead of dCTP, which serves to protect it from restriction endonuclease digestion.

After the template strand of the double-stranded heteroduplex is nicked with an appropriate restriction enzyme, the template strand can be digested with ExoIII nuclease or another appropriate nuclease past the region that contains the site(s) to be mutagenized. The reaction is then stopped to leave a molecule that is only partially single-stranded. A complete double-stranded DNA homoduplex is then formed using DNA polymerase in the presence of all four deoxyribonucleotide triphosphates, ATP, and DNA ligase. This homoduplex molecule can then be transformed into a suitable host cell such as E. coli JM101.

Expression Cassettes of the Invention

To prepare expression cassettes, the recombinant DNA sequence or segment may be circular or linear, double-stranded or single-stranded. Generally, the DNA sequence or segment is in the form of chimeric DNA, such as plasmid DNA or a vector that can also contain coding regions flanked by control sequences that promote the expression of the recombinant DNA present in the resultant transformed cell.

A “chimeric” vector or expression cassette, as used herein, means a vector or cassette including nucleic acid sequences from at least two different species, or has a nucleic acid sequence from the same species that is linked or associated in a manner that does not occur in the “native” or wild type of the species.

Aside from recombinant DNA sequences that serve as transcription units for an RNA transcript, or portions thereof, a portion of the recombinant DNA may be untranscribed, serving a regulatory or a structural function. For example, the recombinant DNA may have a promoter that is active in mammalian cells.

Other elements functional in the host cells, such as introns, enhancers, polyadenylation sequences and the like, may also be a part of the recombinant DNA. Such elements may or may not be necessary for the function of the DNA, but may provide improved expression of the DNA by affecting transcription, stability of the RNA, or the like. Such elements may be included in the DNA as desired to obtain the optimal expression in the cell.

Control sequences are DNA sequences necessary for the expression of an operably linked coding sequence in a particular host organism. The control sequences that are suitable for prokaryotic cells, for example, include a promoter, and optionally an operator sequence, and a ribosome binding site. Eukaryotic cells are known to utilize promoters, polyadenylation signals, and enhancers.

Operably linked nucleic acids are nucleic acids placed in a functional relationship with another nucleic acid sequence. For example, a promoter or enhancer is operably linked to a coding sequence if it affects the transcription of the sequence; or a ribosome binding site is operably linked to a coding sequence if it is positioned so as to facilitate translation. Generally, operably linked DNA sequences are DNA sequences that are linked are contiguous. However, enhancers do not have to be contiguous. Linking is accomplished by ligation at convenient restriction sites. If such sites do not exist, the synthetic oligonucleotide adaptors or linkers are used in accord with conventional practice.

The recombinant DNA to be introduced into the cells may contain either a selectable marker gene or a reporter gene or both to facilitate identification and selection of expressing cells from the population of cells sought to be transfected or infected through viral vectors. In other embodiments, the selectable marker may be carried on a separate piece of DNA and used in a co-transfection procedure. Both selectable markers and reporter genes may be flanked with appropriate regulatory sequences to enable expression in the host cells. Useful selectable markers are known in the art and include, for example, antibiotic-resistance genes, such as neo and the like.

Reporter genes are used for identifying potentially transfected cells and for evaluating the functionality of regulatory sequences. Reporter genes that encode for easily assayable proteins are well known in the art. In general, a reporter gene is a gene that is not present in or expressed by the recipient organism or tissue and that encodes a protein whose expression is manifested by some easily detectable property, e.g., enzymatic activity. For example, reporter genes include the chloramphenicol acetyl transferase gene (cat) from Tn9 of E. coli and the luciferase gene from firefly Photinus pyralis. Expression of the reporter gene is assayed at a suitable time after the DNA has been introduced into the recipient cells.

The general methods for constructing recombinant DNA that can transfect target cells are well known to those skilled in the art, and the same compositions and methods of construction may be utilized to produce the DNA useful herein. For example, Sambrook and Russell, infra, provides suitable methods of construction.

The recombinant DNA can be readily introduced into the host cells, e.g., mammalian, bacterial, yeast or insect cells by transfection with an expression vector composed of DNA encoding the peptide (e.g., CD200 inhibitor) by any procedure useful for the introduction into a particular cell, e.g., physical or biological methods, to yield a cell having the recombinant DNA stably integrated into its genome or existing as a episomal element, so that the DNA molecules, or sequences of the present invention are expressed by the host cell. Preferably, the DNA is introduced into host cells via a vector. The host cell is preferably of eukaryotic origin, e.g., plant, mammalian, insect, yeast or fungal sources, but host cells of non-eukaryotic origin may also be employed.

Physical methods to introduce a preselected DNA into a host cell include calcium phosphate precipitation, lipofection, particle bombardment, microinjection, electroporation, and the like. Biological methods to introduce the DNA of interest into a host cell include the use of DNA and RNA viral vectors. For mammalian gene therapy, as described herein below, it is desirable to use an efficient means of inserting a copy gene into the host genome. Viral vectors, and especially retroviral vectors, have become the most widely used method for inserting genes into mammalian, e.g., human cells. Other viral vectors can be derived from poxviruses, herpes simplex virus I, adenoviruses and adeno-associated viruses, and the like. See, for example, U.S. Pat. Nos. 5,350,674 and 5,585,362.

As discussed above, a “transfected”, “or “transduced” host cell or cell line is one in which the genome has been altered or augmented by the presence of at least one heterologous or recombinant nucleic acid sequence. The host cells of the present invention are typically produced by transfection with a DNA sequence in a plasmid expression vector, a viral expression vector, or as an isolated linear DNA sequence. The transfected DNA can become a chromosomally integrated recombinant DNA sequence, which is composed of sequence encoding the peptide (e.g., a CD200 inhibitor).

To confirm the presence of the recombinant DNA sequence in the host cell, a variety of assays may be performed. Such assays include, for example, “molecular biological” assays well known to those of skill in the art, such as Southern and Northern blotting, RT-PCR and PCR; “biochemical” assays, such as detecting the presence or absence of a particular peptide, e.g., by immunological means (ELISAs and Western blots) or by assays described herein to identify agents falling within the scope of the invention.

To detect and quantitate RNA produced from introduced recombinant DNA segments, RT-PCR may be employed. In this application of PCR, it is first necessary to reverse transcribe RNA into DNA, using enzymes such as reverse transcriptase, and then through the use of conventional PCR techniques amplify the DNA. In most instances PCR techniques, while useful, will not demonstrate integrity of the RNA product. Further information about the nature of the RNA product may be obtained by Northern blotting. This technique demonstrates the presence of an RNA species and gives information about the integrity of that RNA. The presence or absence of an RNA species can also be determined using dot or slot blot Northern hybridizations. These techniques are modifications of Northern blotting and only demonstrate the presence or absence of an RNA species.

While Southern blotting and PCR may be used to detect the recombinant DNA segment in question, they do not provide information as to whether the preselected DNA segment is being expressed. Expression may be evaluated by specifically identifying the peptide products of the introduced recombinant DNA sequences or evaluating the phenotypic changes brought about by the expression of the introduced recombinant DNA segment in the host cell.

The instant invention provides a cell expression system for expressing exogenous nucleic acid material in a mammalian recipient. The expression system, also referred to as a “genetically modified cell”, comprises a cell and an expression vector for expressing the exogenous nucleic acid material. The genetically modified cells are suitable for administration to a mammalian recipient, where they replace the endogenous cells of the recipient. Thus, the preferred genetically modified cells are non-immortalized and are non-tumorigenic.

According to one embodiment, the cells are transfected or otherwise genetically modified ex vivo. The cells are isolated from a mammal (preferably a human), nucleic acid introduced (i.e., transduced or transfected in vitro) with a vector for expressing a heterologous (e.g., recombinant) gene encoding the therapeutic agent, and then administered to a mammalian recipient for delivery of the therapeutic agent in situ. The mammalian recipient may be a human and the cells to be modified are autologous cells, i.e., the cells are isolated from the mammalian recipient.

According to another embodiment, the cells are transfected or transduced or otherwise genetically modified in vivo. The cells from the mammalian recipient are transduced or transfected in vivo with a vector containing exogenous nucleic acid material for expressing a heterologous (e.g., recombinant) gene encoding a therapeutic agent and the therapeutic agent is delivered in situ.

As used herein, “exogenous nucleic acid material” refers to a nucleic acid or an oligonucleotide, either natural or synthetic, which is not naturally found in the cells; or if it is naturally found in the cells, is modified from its original or native form. Thus, “exogenous nucleic acid material” includes, for example, a non-naturally occurring nucleic acid that can be transcribed into a “heterologous gene” (i.e., a gene encoding a protein that is not expressed or is expressed at biologically insignificant levels in a naturally-occurring cell of the same type). To illustrate, a synthetic or natural gene encoding human erythropoietin (EPO) would be considered “exogenous nucleic acid material” with respect to human peritoneal mesothelial cells since the latter cells do not naturally express EPO. Still another example of “exogenous nucleic acid material” is the introduction of only part of a gene to create a recombinant gene, such as combining a regulatable promoter with an endogenous coding sequence via homologous recombination.

Methods for Introducing the Expression Cassettes of the Invention into Cells

The condition amenable to gene therapy may be a prophylactic process, i.e., a process for preventing disease or an undesired medical condition. Thus, the instant invention embraces a system for delivering peptides, such as CD200 inhibitors, that have a prophylactic function (i.e., a prophylactic agent) to the mammalian recipient.

The nucleic acid material (e.g., an expression cassette encoding a CD200 inhibitor peptide) can be introduced into the cell ex vivo or in vivo by genetic transfer methods, such as transfection or transduction, to provide a genetically modified cell. Various expression vectors (i.e., vehicles for facilitating delivery of exogenous nucleic acid into a target cell) are known to one of ordinary skill in the art.

As used herein, “transfection of cells” refers to the acquisition by a cell of new nucleic acid material by incorporation of added DNA. Thus, transfection refers to the insertion of nucleic acid into a cell using physical or chemical methods. Several transfection techniques are known to those of ordinary skill in the art including calcium phosphate DNA co-precipitation, DEAE-dextran, electroporation, cationic liposome-mediated transfection, tungsten particle-facilitated microparticle bombardment, and strontium phosphate DNA co-precipitation.

In contrast, “transduction of cells” refers to the process of transferring nucleic acid into a cell using a DNA or RNA virus. A RNA virus (i.e., a retrovirus) for transferring a nucleic acid into a cell is referred to herein as a transducing chimeric retrovirus. Exogenous nucleic acid material contained within the retrovirus is incorporated into the genome of the transduced cell. A cell that has been transduced with a chimeric DNA virus (e.g., an adenovirus carrying a cDNA encoding a therapeutic agent), will not have the exogenous nucleic acid material incorporated into its genome but will be capable of expressing the exogenous nucleic acid material that is retained extrachromosomally within the cell.

The exogenous nucleic acid material can include the nucleic acid encoding the peptide together with a promoter to control transcription. The promoter characteristically has a specific nucleotide sequence necessary to initiate transcription. The exogenous nucleic acid material may further include additional sequences (i.e., enhancers) required to obtain the desired gene transcription activity. For the purpose of this discussion an “enhancer” is simply any non-translated DNA sequence that works with the coding sequence (in cis) to change the basal transcription level dictated by the promoter. The exogenous nucleic acid material may be introduced into the cell genome immediately downstream from the promoter so that the promoter and coding sequence are operatively linked so as to permit transcription of the coding sequence. An expression vector can include an exogenous promoter element to control transcription of the inserted exogenous gene. Such exogenous promoters include both constitutive and regulatable promoters.

Naturally-occurring constitutive promoters control the expression of essential cell functions. As a result, a nucleic acid sequence under the control of a constitutive promoter is expressed under all conditions of cell growth. Constitutive promoters include the promoters for the following genes which encode certain constitutive or “housekeeping” functions: hypoxanthine phosphoribosyl transferase (HPRT), dihydrofolate reductase (DHFR), adenosine deaminase, phosphoglycerol kinase (PGK), pyruvate kinase, phosphoglycerol mutase, the beta-actin promoter, and other constitutive promoters known to those of skill in the art. In addition, many viral promoters function constitutively in eukaryotic cells. These include: the early and late promoters of SV40; the long terminal repeats (LTRs) of Moloney Leukemia Virus and other retroviruses; and the thymidine kinase promoter of Herpes Simplex Virus, among many others.

Nucleic acid sequences that are under the control of regulatable promoters are expressed only or to a greater or lesser degree in the presence of an inducing or repressing agent, (e.g., transcription under control of the metallothionein promoter is greatly increased in presence of certain metal ions). Regulatable promoters include responsive elements (REs) that stimulate transcription when their inducing factors are bound. For example, there are REs for serum factors, steroid hormones, retinoic acid, cyclic AMP, and tetracycline and doxycycline. Promoters containing a particular RE can be chosen in order to obtain a regulatable response and in some cases, the RE itself may be attached to a different promoter, thereby conferring regulatability to the encoded nucleic acid sequence. Thus, by selecting the appropriate promoter (constitutive versus regulatable; strong versus weak), it is possible to control both the existence and level of expression of a nucleic acid sequence in the genetically modified cell. If the nucleic acid sequence is under the control of an regulatable promoter, delivery of the therapeutic agent in situ is triggered by exposing the genetically modified cell in situ to conditions for permitting transcription of the nucleic acid sequence, e.g., by intraperitoneal injection of specific inducers of the regulatable promoters which control transcription of the agent. For example, in situ expression of a nucleic acid sequence under the control of the metallothionein promoter in genetically modified cells is enhanced by contacting the genetically modified cells with a solution containing the appropriate (i.e., inducing) metal ions in situ.

Accordingly, the amount of peptide (e.g., a CD200 inhibitor) generated in situ is regulated by controlling such factors as the nature of the promoter used to direct transcription of the nucleic acid sequence, (i.e., whether the promoter is constitutive or regulatable, strong or weak) and the number of copies of the exogenous nucleic acid sequence encoding the peptide that are in the cell.

In one embodiment of the present invention, an expression cassette may contain a pol II promoter that is operably linked to a nucleic acid sequence encoding a peptide (e.g., a CD200 inhibitor). Thus, the pol II promoter, i.e., a RNA polymerase II dependent promoter, initiates the transcription of the RNA, which encodes the peptide of interest. In another embodiment, the pol II promoter is regulatable.

A pol II promoter may be used in its entirety, or a portion or fragment of the promoter sequence may be used in which the portion maintains the promoter activity. As discussed herein, pol II promoters are known to a skilled person in the art and include the promoter of any protein-encoding gene, e.g., an endogenously regulated gene or a constitutively expressed gene. For example, the promoters of genes regulated by cellular physiological events, e.g., heat shock, oxygen levels and/or carbon monoxide levels, e.g., in hypoxia, may be used in the expression cassettes of the invention. In addition, the promoter of any gene regulated by the presence of a pharmacological agent, e.g., tetracycline and derivatives thereof, as well as heavy metal ions and hormones may be employed in the expression cassettes of the invention. In an embodiment of the invention, the pol II promoter can be the CMV promoter or the RSV promoter. In another embodiment, the pol II promoter is the CMV promoter.

As discussed above, a pol II promoter of the invention may be one naturally associated with an endogenously regulated gene or sequence, as may be obtained by isolating the 5′ non-coding sequences located upstream of the coding segment and/or exon. The pol II promoter of the expression cassette can be, for example, the same pol II promoter driving expression of the targeted gene of interest. Alternatively, the nucleic acid sequence encoding the peptide may be placed under the control of a recombinant or heterologous pol II promoter, which refers to a promoter that is not normally associated with the targeted gene's natural environment. Such promoters include promoters isolated from any eukaryotic cell, and promoters not “naturally occurring,” i.e., containing different elements of different transcriptional regulatory regions, and/or mutations that alter expression. In addition to producing nucleic acid sequences of promoters synthetically, sequences may be produced using recombinant cloning and/or nucleic acid amplification technology, including PCR™, in connection with the compositions disclosed herein (see U.S. Pat. No. 4,683,202, U.S. Pat. No. 5,928,906, each incorporated herein by reference).

In one embodiment, a pol II promoter that effectively directs the expression of the RNA in the cell type, organelle, and organism chosen for expression will be employed. Those of ordinary skill in the art of molecular biology generally know the use of promoters for protein expression, for example, see Sambrook and Russell (2001), incorporated herein by reference. The promoters employed may be constitutive, tissue-specific, inducible, and/or useful under the appropriate conditions to direct high level expression of the introduced DNA segment, such as is advantageous in the large-scale production of recombinant proteins and/or peptides. The identity of tissue-specific promoters, as well as assays to characterize their activity, is well known to those of ordinary skill in the art.

In addition to at least one promoter and at least one heterologous nucleic acid sequence encoding the peptide, the expression vector may include a selection gene, for example, a neomycin resistance gene, for facilitating selection of cells that have been transfected or transduced with the expression vector.

Cells can also be transfected with two or more expression vectors, at least one vector containing the nucleic acid sequence(s) encoding the peptide(s), the other vector containing a selection gene. The selection of a suitable promoter, enhancer, selection gene and/or signal sequence is deemed to be within the scope of one of ordinary skill in the art without undue experimentation.

The following discussion is directed to various utilities of the instant invention. For example, the instant invention has utility as an expression system suitable for expressing a peptide described herein.

The instant invention also provides methods for genetically modifying cells of a mammalian recipient in vivo. According to one embodiment, the method comprises introducing an expression vector for expressing a peptide described herein in cells of the mammalian recipient in situ by, for example, injecting the vector into the recipient.

Delivery Vehicles for the Expression Cassettes of the Invention

Delivery of compounds into tissues and across the blood-brain barrier can be limited by the size and biochemical properties of the compounds. Currently, efficient delivery of compounds into cells in vivo can be achieved only when the molecules are small (usually less than 600 Daltons). Gene transfer for the treatment of cancer has been accomplished with recombinant adenoviral vectors.

The selection and optimization of a particular expression vector for expressing a specific peptide (e.g., a CD200 inhibitor) in a cell can be accomplished by obtaining the nucleic acid sequence encoding the peptide, possibly with one or more appropriate control regions (e.g., promoter, insertion sequence); preparing a vector construct comprising the vector into which is inserted the nucleic acid sequence encoding the peptide; transfecting or transducing cultured cells in vitro with the vector construct; and determining whether the peptide is present in the cultured cells.

Vectors for cell gene therapy include viruses, such as replication-deficient viruses (described in detail below). Exemplary viral vectors are derived from Harvey Sarcoma virus, ROUS Sarcoma virus, (MPSV), Moloney murine leukemia virus and DNA viruses (e.g., adenovirus).

Replication-deficient retroviruses are capable of directing synthesis of all virion proteins, but are incapable of making infectious particles. Accordingly, these genetically altered retroviral expression vectors have general utility for high-efficiency transduction of nucleic acid sequences in cultured cells, and specific utility for use in the method of the present invention. Such retroviruses further have utility for the efficient transduction of nucleic acid sequences into cells in vivo. Retroviruses have been used extensively for transferring nucleic acid material into cells. Protocols for producing replication-deficient retroviruses (including the steps of incorporation of exogenous nucleic acid material into a plasmid, transfection of a packaging cell line with plasmid, production of recombinant retroviruses by the packaging cell line, collection of viral particles from tissue culture media, and infection of the target cells with the viral particles) are well known in the art.

An advantage of using retroviruses for gene therapy is that the viruses insert the nucleic acid sequence encoding the peptide into the host cell genome, thereby permitting the nucleic acid sequence encoding the peptide to be passed on to the progeny of the cell when it divides. Promoter sequences in the LTR region have can enhance expression of an inserted coding sequence in a variety of cell types. Some disadvantages of using a retrovirus expression vector are (1) insertional mutagenesis, i.e., the insertion of the nucleic acid sequence encoding the peptide into an undesirable position in the target cell genome which, for example, leads to unregulated cell growth and (2) the need for target cell proliferation in order for the nucleic acid sequence encoding the peptide carried by the vector to be integrated into the target genome.

Another viral candidate useful as an expression vector for transformation of cells is the adenovirus, a double-stranded DNA virus. The adenovirus is infective in a wide range of cell types, including, for example, muscle and endothelial cells.

Adenoviruses (Ad) are double-stranded linear DNA viruses with a 36 kb genome. Several features of adenovirus have made them useful as transgene delivery vehicles for therapeutic applications, such as facilitating in vivo gene delivery. Recombinant adenovirus vectors have been shown to be capable of efficient in situ gene transfer to parenchymal cells of various organs, including the lung, brain, pancreas, gallbladder, and liver. This has allowed the use of these vectors in methods for treating inherited genetic diseases, such as cystic fibrosis, where vectors may be delivered to a target organ. In addition, the ability of the adenovirus vector to accomplish in situ tumor transduction has allowed the development of a variety of anticancer gene therapy methods for non-disseminated disease. In these methods, vector containment favors tumor cell-specific transduction.

Like the retrovirus, the adenovirus genome is adaptable for use as an expression vector for gene therapy, i.e., by removing the genetic information that controls production of the virus itself. Because the adenovirus functions in an extrachromosomal fashion, the recombinant adenovirus does not have the theoretical problem of insertional mutagenesis.

Several approaches traditionally have been used to generate the recombinant adenoviruses. One approach involves direct ligation of restriction endonuclease fragments containing a nucleic acid sequence of interest to portions of the adenoviral genome. Alternatively, the nucleic acid sequence of interest may be inserted into a defective adenovirus by homologous recombination results. The desired recombinants are identified by screening individual plaques generated in a lawn of complementation cells.

Most adenovirus vectors are based on the adenovirus type 5 (Ad5) backbone in which an expression cassette containing the nucleic acid sequence of interest has been introduced in place of the early region 1 (E1) or early region 3 (E3). Viruses in which E1 has been deleted are defective for replication and are propagated in human complementation cells (e.g., 293 or 911 cells), which supply the missing gene E1 and pIX in trans.

In one embodiment of the present invention, one will desire to generate the peptide (e.g., a CD200 inhibitor) in a CNS cancer tumor (e.g, a glioma). A suitable vector for this application is an FIV vector or an AAV vector. For example, one may use AAV5. Also, one may apply poliovirus or HSV vectors.

Recombinant adenovirus, adeno-associated virus (AAV) and feline immunodeficiency virus (FIV) can be used to deliver genes in vitro and in vivo. Each has its own advantages and disadvantages. Adenoviruses are double stranded DNA viruses with large genomes (36 kb) and have been engineered to accommodate expression cassettes in distinct regions.

Adeno-associated viruses have encapsidated genomes, similar to Ad, but are smaller in size and packaging capacity (˜30 nm vs. ˜100 nm; packaging limit of ˜4.5 kb). AAV contain single stranded DNA genomes of the + or the − strand. Eight serotypes of AAV (1-8) have been studied extensively, three of which have been evaluated in the brain. An important consideration for the present application is that AAV5 transduces striatal and cortical neurons, and is not associated with any known pathologies.

FIV is an enveloped virus with a strong safety profile in humans; individuals bitten or scratched by FIV-infected cats do not seroconvert and have not been reported to show any signs of disease. Like AAV, FIV provides lasting transgene expression in mouse and nonhuman primate neurons, and transduction can be directed to different cell types by pseudotyping, the process of exchanging the viruses' native envelope for an envelope from another virus.

Thus, as will be apparent to one of ordinary skill in the art, a variety of suitable viral expression vectors are available for transferring exogenous nucleic acid material into cells. The selection of an appropriate expression vector to express a therapeutic agent for a particular condition amenable to gene therapy and the optimization of the conditions for insertion of the selected expression vector into the cell, are within the scope of one of ordinary skill in the art without the need for undue experimentation.

In another embodiment, the expression vector is in the form of a plasmid, which is transferred into the target cells by one of a variety of methods: physical (e.g., microinjection, electroporation, scrape loading, microparticle bombardment) or by cellular uptake as a chemical complex (e.g., calcium or strontium co-precipitation, complexation with lipid, complexation with ligand). Several commercial products are available for cationic liposome complexation including Lipofectin™ (Gibco-BRL, Gaithersburg, Md.) and Transfectam™ (ProMega, Madison, Wis.). However, the efficiency of transfection by these methods is highly dependent on the nature of the target cell and accordingly, the conditions for optimal transfection of nucleic acids into cells using the above-mentioned procedures must be optimized. Such optimization is within the scope of one of ordinary skill in the art without the need for undue experimentation.

Certain embodiments of the invention will now be illustrated by the following non-limiting Examples.

Example 1 Determination of how Select Inhibitors Reverse CD200-Induced Immune Suppression in Sentinel Lymph Nodes

Tumor-associated microenvironments and the sentinel lymph nodes exist under immunosuppressive conditions that inhibit the ability of the immune system to eliminate cancer cells and prevent reoccurrence. While researchers have generated signaling pathway inhibitors to overcome immunosuppressive cascades in either cancer or immune cells, or both, little efficacy has been achieved. CD200 is an immunosuppressive protein that negatively regulates immune cells bearing the CD200R. Recently, it has been reported that CD200 contains domains that act as competitive inhibitors modulating/reversing the suppressive properties of the protein.

As described herein, the ability of these inhibitors to modulate/reverse the suppressive properties of the tumor microenvironment has been demonstrated. Described herein are studies designed to: i) optimize the inhibitors, ii) evaluate CD200/CD200R interactions on the ability of dendritic cells to present antigen, iii), and determine the CD200 derived competitive inhibitors mechanism(s) of action.

When cancer is detected in the clinic, patients are generally immunosuppressed due to the generation of immunosuppressive conditions in tumor-associated microenvironments. Immunosuppressive cells, such as myeloid-derived suppressor cells and regulatory T cells show increased activity while dendritic cells (DCs) appear to be impaired in tumors and sentinel lymph nodes in cancer patients. Because of the unique isoforms of CD200 receptors expressed on T cells (Wright et al., J Immunol 2003; 171(6): 3034-46; Gorczynski et al., J Immunol 2000; 165(9): 4854-60; Gorczynski et al., J Immunol 2004; 172(12): 7744-9), CD200/CD200R interactions are proposed to exert both direct and indirect effects on T cell activation. Although multiple graft rejection studies have determined CD200 to be immunosuppressive, Gorczynski et. al. reported that specific peptide domains within the CD200 protein have agonist (exhibit the same immune-suppressive effects) or antagonist (act as competitive inhibitors for CD200) activity for the CD200R (Gorczynski et al., J Surg Res 2008; 145(1): 87-96).

Gorczynski et. al. described agonist and antagonist peptides derived from CD200. To determine if agonist peptides mimicked immune suppression elicited by intact CD200, select agonists were mixed with OVA and wildtype (non-tumor-bearing) CD57BL/6 mice were immunized in a prime-boost model (Ohlfest et al., J Immunol 2013; 190(2): 613-20). These CD200-derived agonists suppressed antigen-specific CD8⁺ T cell proliferative responses in non-tumor-bearing mice to levels equivalent to those routinely seen in tumor-bearing mice (FIG. 11a ). These data support the proposal that CD200 suppresses antigen-specific CD8⁺ T cell responses as described herein.

Whether the different antagonists described by Gorczynski et. al. (J Surg Res 2008; 145(1): 87-96) could modulate or reverse the suppressive effects of the tumor microenvironment was also investigated. It was concluded that different antagonists either act through different CD200R isoforms or have different biological effects on the same receptor. These conclusions were supported by experiments where splenocytes were pulsed with OVA+selected CD200R antagonists (6061, 6069, 4004, 4006, 4013) for 24 hours. The splenocytes were then washed and cultured for 48 hours with the addition of OT-1 T cells. The cultures were then assessed for cytokine production using a flow cytometric bead array. It was found that different cytokine profiles were elicited by antagonists 4004 and 4006 compared to the others (FIGS. 11a and 11b ).

Whether the CD200R antagonists were capable of modulating/reversing the suppressive effects the tumor exhibits in the cervical lymph nodes was subsequently investigated. It was concluded that the addition of an antagonist reversed tumor induced suppression. This conclusion was determined by vaccinating mice with OVA+ the peptide 6059 in a prime boost model Ohlfest et. al., (J Immunol 2013; 190(2): 613-20 (FIG. 12a ). We demonstrated a strong suppressive effect as routinely seen in tumor-bearing mice (FIG. 12a ). To validate our observations, lymphocytes were harvested from the cervical lymph nodes of the antagonist 6059 treated mice and restimulated with the OVA peptide SIINFEKL (SEQ ID NO: 11). After 48 hrs, the culture supernatant was analyzed for cytokine production demonstrating the ability of the antagonist to modulate/reverse glioma-induced suppression (FIG. 12b ). Interestingly, vaccinating non-tumor bearing mice with OVA+glioma-derived exosomes+ the antagonist 6059 partially reversed the suppression induced by exosomes (FIG. 12C). These experiments support the hypothesis that exosomes express the CD200 protein thereby inhibiting the ability to prime a T cell response in the draining lymph nodes of glioma bearing mice. Other antagonists were similarly evaluated.

Whether vaccination with CD200R antagonists could enhance the survival of tumor-bearing mice was also studied. It was concluded that the addition of the antagonists enhances survival benefit in the GL261 model (FIG. 13A). GL261 tumor bearing mice were vaccinated weekly with saline, tumor lysates (TL) or tumor lysates+an antagonist (4004, 4013, 6059). These experiments show that tumors grow faster in mice vaccinated with saline or tumor lysate alone compared to mice vaccinated with tumor lysate plus an antagonist (data not shown) resulting in an increased survival benefit in the GL261 (FIG. 13A) model. These results translated to a breast carcinoma (EMT6) model (FIG. 13B) tumor model.

Optimization of the Competitive Inhibitors

One of the major hurdles in cancer immunotherapy is overcoming immunosuppression in both the tumor microenvironment and sentinel lymph nodes. Described herein is the optimization of the CD200 peptide domains to overcome tumor-induced immunosuppression in both the sentinel lymph nodes and the tumor microenvironment.

Using mixed leukocyte reactions, Gorczynski et al (J Surg Res 2008; 145(1): 87-96) reported that specific regions of the CD200 protein act as agonists or act as antagonists (also described herein as “CD200 inhibitors”). Mice express five isoforms of the CD200R that exhibit tissue-restricted expression and heterogeneity of function (Wright G J, Cherwinski H, Foster-Cuevas M, et al. Characterization of the CD200 receptor family in mice and humans and their interactions with CD200. J Immunol 2003; 171(6): 3034-46; Gorczynski R, Boudakov I, Khatri I. Peptides of CD200 modulate LPS-induced TNF-alpha induction and mortality in vivo. J Surg Res 2008; 145(1): 87-96; Gorczynski R, Chen Z, Kai Y, Lee L, Wong S, Marsden P A. CD200 is a ligand for all members of the CD200R family of immunoregulatory molecules. J Immunol 2004; 172(12): 7744-9; Gorczynski R M, Chen Z, Clark D A, et al. Structural and functional heterogeneity in the CD200R family of immunoregulatory molecules and their expression at the feto-maternal interface. Am J Reprod Immunol 2004; 52(2): 147-63). The different inhibitors may work through different receptors resulting in different biologic responses. The experiments described herein determine if the different inhibitors work through alternative pathways allowing the potential use of multiple inhibitors that may synergize with each other, thereby enhancing the ability to induce a tumoricidal response.

Methods:

Since mice have five identified CD200Rs, we need to determine if the CD200-derived peptide inhibitors function through multiple receptors. Accordingly, wildtype splenocytes will be blocked using anti-CD200R1, anti-CD200R2, anti-CD200R3, or anti-CD200R1 (Gorczynski R, Lee L, Boudakov I. Augmented Induction of CD4+ CD25+ Treg using Monoclonal Antibodies to CD200R. Transplantation 2005; 79: 1180-83). Following incubation, cells are pulsed with OVA+PoIy:ICLC in the presence or absence of recombinant mouse CD200Fc chimeric protein (rmCD200Fc, R&D Systems) with or without the addition of the individual peptides. Following a 24 hr incubation, purified OT-I CD8 T cells are added for 48 hr and then the supernatants are analyzed for Th1/Th2 cytokines using a flow cytometric bead array and TGFβ production by ELISA. To determine the effects the inhibitors have on restoration of a proliferative response, splenocytes are pulsed from wildtype mice with the same treatment groups as described above. Following a 24 hr incubation, purified CFSE labeled OT-I CD8 T cells are added to the cells. After 48 h incubation cells are analyzed by flow cytometry for proliferation. If appropriate, peptides are combined into a mixture to determine if blocking CD200 binding to multiple receptors enhances the immune response.

In summary, blood and cervical node lymphocytes are analyzed for SIINFEKL/K^(b) specific CD8⁺ T cells (‘SIINFEKL’ disclosed as SEQ ID NO: 11). Lymphocytes isolated from cervical lymph nodes are stimulated with a peptide containing the core OVA-derived SIINFEKL epitope (SEQ ID NO: 11) (EVSQLEQLESIINFEKLTEEWTSSNVM) (SEQ ID NO: 12). Supernatants are analyzed using a flow cytometric bead array (BD Bioscience) for the levels of Th1, Th2, and Th17 cytokines. A commercial ELISA assay (R&D Systems) is used to measure levels of TGFβ produced. A separate aliquot of cells is analyzed for surface expression of CD8 and SIINFEKL/K^(b) binding (‘SIINFEKL’ disclosed as SEQ ID NO: 11) and intracellular expression IFN-γ¹.

Evaluate CD200/CD200R Interactions on the Ability of Dendritic Cells to Present Antigen.

Dendritic cells (DCs) are the most powerful known antigen-presenting cells. Dendritic cells patrol the tissues of the body for pathogens and signs of damage. Upon injection, tumor cells or cell components are taken up and processed by DCs in the skin and secondary lymphoid organs, which then bridge innate and adaptive immunity. CD200 binds to the CD200R on dendritic cells altering their functional response (Li Y, Zhao L D, Tong L S, et al. Aberrant CD200/CD200R1 expression and function in systemic lupus erythematosus contributes to abnormal T-cell responsiveness and dendritic cell activity. Arthritis Res Ther 2012; 14(3): R123).

Purified bone marrow derived DCs (BMDCs) are used for murine studies. Experimental endpoints include: i) co-stimulatory marker expression, ii) OVA cross presentation, and iii) cytokine production. To investigate the ability to translate to humans, iDC are pulsed with the CMV peptide pp65+hCD200Fc+/−inhibitor. Experimental endpoints include i) co-stimulatory marker expression and ii) cytokine production.

In summary, BMDCs are maturated using a protocol modified from Inaba et al. (Ohlfest J R, Andersen B M, Litterman A J, et al. Vaccine injection site matters: qualitative and quantitative defects in CD8 T cells primed as a function of proximity to the tumor in a murine glioma model. J Immunol 2013; 190(2): 613-20; Wick D A, Martin S D, Nelson B H, Webb J R. Profound CD8+ T cell immunity elicited by sequential daily immunization with exogenous antigen plus the TLR3 agonist poly(I:C). Vaccine 2011; 29(5): 984-93). Briefly, femurs and tibias are removed from C57BL/6 mice and flushed with PBS. Cells are washed and plated in complete RPMI 1640 containing 20 ng/mL GM-CSF. Non-adherent cells are removed and media replaced every three days. Six days post-bone, loosely adherent cells are harvested, washed and plated in 96 well plates at 100,000 cells/200 μl per well. Cells are pulsed with OVA+CpG, OVA+CpG+mCD200Fc, OVA+CpG+inhibitor, or OVA+CpG+CD200Fc+inhibitor. CD200Fc is given 30 minutes prior to pulsing. Non-pulsed wells are used as a control. Following 24 hr incubation, dendritic cells are stained with antibodies to CD11c, CD86, CD80, and HLA-II and analyzed by flow cytometry. Supernatants are analyzed for IL-6 and IL-12 production. To test for the effects of CD200 on OVA cross presentation, DCs are stained with 25-D1.16 to measure antigen expression. 25-D1.16 is a monoclonal antibody that specifically binds SIINFEKL (SEQ ID NO: 11) only when presented by H-2K^(b). 5×10⁵ HLA-A2⁺ immature DCs derived from CD14⁺ peripheral blood monocytes are pulsed with 10 μg of the CMV peptide pp65₄₉₅₋₅₀₃(NLVPMVATV (SEQ ID NO: 13))+/−hCD200Fc+/−inhibitor.

Determine the CD200 Derived Competitive Inhibitors Mechanism(s).

It has been demonstrated using a prime boost model that the inhibitor peptide 6059 reversed the suppressive effects in tumor-bearing mice.

In the following experiments, wildtype mice are inoculated with GL261 cells and vaccinated as shown in FIG. 14. Mice will be vaccinated with i) saline, ii) 65 μg of GL261 tumor lysate tumor lysate, or iii) 65 μg of GL261 tumor lysate tumor lysates+optimized Inhibitors. Experiments are performed as described above. We will study the effects of our novel inhibitors on: i) T cell expansion, ii) cytokine response and iii) cytolytic response observed in the cervical lymph nodes, iv) lymphocyte infiltration and caspase 3/7 activity, v) development of immunological memory, and vi) survival benefit. Moreover, this work is translated to our human T cell response using a CMV assay as described by Olin et al. (Olin M R, Andersen B M, Litterman A J, et al. Oxygen is a master regulator of the immunogenicity of primary human glioma cells. Cancer Res 2011; 71(21): 6583-9).

In summary, the effects on T cells is studied by measuring SIINFEKL (SEQ ID NO: 11) specific T cell expansion, recall response measured by cytokine production and the generation of a CTL response. Moreover, mice (n=10/treatment group) are inoculated with luciferase-expressing GL261 glioma cells as described and vaccinated with i) saline, ii) tumor lysate, or iii) tumor lysates+optimized inhibitors on days 3, 10, 17, 24, and 31. In a separate experiment, a group of mice (n=6) are sacrificed on days 7 and 14. Brains are harvested and analyzed by immunohistochemistry for CD3 infiltration and active caspase activity as described by Olin et al. (Olin M R, Andersen B M, Zellmer D M, et al. Superior efficacy of tumor cell vaccines grown in physiologic oxygen. Clin Cancer Res 2010; 16(19): 4800-8). In a second group of mice (n=5), brain infiltrating lymphocytes will be harvested as previously described (Ohlfest J R, Andersen B M, Litterman A J, et al. Vaccine injection site matters: qualitative and quantitative defects in CD8 T cells primed as a function of proximity to the tumor in a murine glioma model. J Immunol 2013; 190(2): 613-20) and phenotyped for CD4 or CD8 populations. In addition, mice are imaged weekly and monitored for survival. Following survival (100 days post inoculation), mice are re-inoculated with GL261 in the contralateral hemisphere and followed for survival. Newly inoculated mice (no vaccination) are used as a control. Further, 5×10⁵ HLA-A2⁺ CMV immature DCs derived from CD14⁺ peripheral blood monocytes are pulsed with 10 μg of the CMV peptide pp65₄₉₅₋₅₀₃(NLVPMVATV (SEQ ID NO: 13))+/−hCD200Fc or OVA+CD200Fc+inhibitor. Cells are matured as described previously (Olin M R, Andersen B M, Litterman A J, et al. Oxygen is a master regulator of the immunogenicity of primary human glioma cells. Cancer Res 2011; 71(21): 6583-9; Inaba K, Inaba M, Romani N, et al. Generation of large numbers of dendritic cells from mouse bone marrow cultures supplemented with granulocyte/macrophage colony-stimulating factor. J Exp Med 1992; 176(6): 1693-702). Following maturation, 5×10⁵ PBMCs from same donor are added and cultured for 48 hours. Supernatants are analyzed for IFNγ and granzyme B production by cytometric bead array (BD Biosciences) (Olin M R, Andersen B M, Litterman A J, et al. Oxygen is a master regulator of the immunogenicity of primary human glioma cells. Cancer Res 2011; 71(21): 6583-9). CMV sera-negative PBMCs is used as a control. All experiments are run in triplicate. The ANOVA analysis of the data is performed using the Bonferroni multiple comparison test (with control), as well as the Dunnett's two-sided multiple comparison test (also with control), for parametric variables, and in the case of non-parametric variables, using the Kruskal-Wallis ANOVA with the Kruskal-Wallis multiple comparison z-value test (Dunn's test).

Example 2 Overcoming the Immunosuppressive Effects of the Tumor Microenvironment within the Central Nervous System

Even if the inhibitors are used to prime a T cell response in lymph nodes, the activated T cells encounter an immunosuppressive tumor microenvironment. To alleviate this hurdle, suppression of the tumor effects in the microenvironment is sought.

Patients with glioblastoma exhibit systemic immune suppression effecting resulting in deficient adaptive immune responses. These deficiencies are due to the enriched immunosuppressive factors secreted by the tumor suppressing T cell proliferation and cytotoxic function Immunosuppression plays an important role in tumor progression in patients with glioblastoma. Reversing immune suppression to provide an effective immune targeting allows patients with glioma to have less tumor progression and improved outcomes.

It has been found that the inhibitors can reverse or modulate the immunosuppressive tumor microenvironment. Tumor-bearing mice were inoculated in the brain with 10 μg of the inhibitor 6059 at the same coordinates at which the tumor was injected two days previously. This was followed by weekly injections of tumor lysate+inhibitor (FIG. 5). Tumor growth was delayed in mice receiving the 6059 inhibitor.

The inventors have been focusing on CD200 competitive inhibitors to overcome the suppressive effects of the tumor in the draining lymph nodes. However, even if a tumoricidal response is enhanced, the suppressive properties of the tumor microenvironment decreases the cytolytic response.

The optimized CD200 antagonist peptide is tested in the CNS of tumor bearing mice. 15,000 luciferase expressing GL261 cells are inoculated as described above. Adenovirus is inoculated using the same coordinates as tumor on day 2 post glioma inoculation. On day 4, mice are vaccinated subcutaneously in the back of the neck with a combination of i) tumor lysates+Poly:ICLC (tumor lysate column), ii) inhibitors with tumor lysates+Poly:ICLC (with vaccine column) or iii) adenovirus in the CNS (in CNS column) as outlined in Table 3.

TABLE 3 Tumor Lysate With vaccine In CNS Group 1 − − − Group 2 + − − Group 3 + + − Group 4 + − + Group 5 + + +

All mice receiving tumor lysates receive Poly:ICLC as an adjuvant. As a positive control, a group of mice receive the inhibitors using Alzet pumps infusing the inhibitor at a constant concentration of 1 μg/μL at a rate of 0.5 μL/hr into the tumor environment. Experiments are performed as described above, and it is determined what are the effects of the novel inhibitors on: i) lymphocyte infiltration and caspase 3/7 activity, ii) development of immunological memory, and iii) survival.

A constant delivery system of novel inhibitor into the CNS maintaining an environment favorable for the immune system is developed. An adenovirus vector is generated that encodes selected inhibitor(s). The vectors used in this study are first generation, replication-deficient, recombinant adenovirus type 5 vectors (Ad), with deletions in the E1 and E3 regions. The expression cassette containing the transgene will be inserted within the E1 region (Southgate T, Kroeger K M, Liu C, Lowenstein P R, Castro M G. Gene transfer into neural cells in vitro using adenoviral vectors. Curr Protoc Neurosci 2008; Chapter 4: Unit 4 23). The Ad vector encoding the optimized inhibitor to be secreted into the tumor microenvironment is constructed, scaled up and purified. Transgene expression is under the control of the human CMV promoter (Curtin J F, King G D, Barcia C, et al. Fms-like tyrosine kinase 3 ligand recruits plasmacytoid dendritic cells to the brain. J Immunol 2006; 176(6): 3566-77; Ali S, King G D, Curtin J F, et al. Combined immunostimulation and conditional cytotoxic gene therapy provide long-term survival in a large glioma model. Cancer Res 2005; 65(16): 7194-204). All viral preparations is tested to be free of replication-competent adenovirus (RCA) and lipopolysaccharide (LPS) contamination using methodologies previously described (Puntel M, Kroeger K M, Sanderson N S, Thomas C E, Castro M G, Lowenstein P R. Gene transfer into rat brain using adenoviral vectors. Curr Protoc Neurosci 2010; Chapter 4: Unit 4 24; King G D, Muhammad A K, Curtin J F, et al. Flt3L and TK gene therapy eradicate multifocal glioma in a syngeneic glioblastoma model. Neuro Oncol 2008; 10(1): 19-31). The efficacy of Ads to express transgenes within the tumor microenvironment in rat and mouse intracranial, syngeneic GBM models has been extensively tested and validated. The present data indicate that using Ads delivered directly into the tumor mass, it is possible to achieve widespread and stable therapeutic transgene expression, elicit tumor regression and long-term anti-GBM immunological memory (Ghulam Muhammad A K, Candolfi M, King G D, et al. Antiglioma immunological memory in response to conditional cytotoxic/immune-stimulatory gene therapy: humoral and cellular immunity lead to tumor regression. Clin Cancer Res 2009; 15(19): 6113-27; Candolfi M, Yagiz K, Foulad D, et al. Release of HMGB1 in response to proapoptotic glioma killing strategies: efficacy and neurotoxicity. Clin Cancer Res 2009; 15(13): 4401-14; curtin J F, Liu N, Candolfi M, et al. HMGB1 mediates endogenous TLR2 activation and brain tumor regression. PLoS Med 2009; 6(1): e10; Curtin J F, Candolfi M, Fakhouri T M, et al. Treg depletion inhibits efficacy of cancer immunotherapy: implications for clinical trials. PLoS One 2008; 3(4): e1983).

Example 3 CD200 in Glioma-Induced Immunosuppression The Role for CD200 Pathway Blockade in Targeted Immunotherapy

Introduction.

Glioblastoma multiforme (GBM) is the most common malignant brain tumor in adults and is incurable with a 5-year survival rate of approximately 30%¹⁻³. Currently, there is no cure for pediatric high grade gliomas such as diffuse intrinsic pontine glioma; 90% of children with this malignancy die within 2 years⁴. While vaccine-based clinical trials for gliomas have succeeded in slowing tumor growth by inducing CD8 T-cell mediated anti-tumor responses, they have not significantly increased overall survival^(5, 6). These trials suggest that a major limitation to their success may be tumor-induced immune suppression.

Immune suppression occurs naturally via multiple mechanisms^(7, 8). These mechanisms serve an important role by resolving inflammation returning tissue microenvironments to homeostasis. There is clear evidence now that many tumors employ various immunosuppressive mechanisms to evade immune surveillance promoting tumorigenesis. Arguably the two most studied immune inhibitory receptors are cytotoxic T lymphocyte antigen 4 and programmed cell death protein 1, both of which are expressed on effector T-cells^(9, 10). Monoclonal antibodies specific for these receptors extend survival in subsets of cancer patients, presumably by blocking ligand binding to these receptors and preventing inhibition of T-cell effector functions¹⁰. These striking clinical results suggest that brain tumor immunotherapy would benefit by the identification and subsequent blockade of immune inhibitory pathways in the central nervous system.

An immune inhibitory ligand/receptor pair that helps maintain immune quiescence in the CNS is CD200/CD200R¹¹. CD200 (OX2) is a highly expressed membrane glycoprotein with a broad tissue distribution. In the CNS, CD200 is expressed predominantly by neurons^(11, 12) down-modulating the activation state of perivascular macrophages and microglia through CD200R¹³. Mice express five CD200R isoforms that exhibit tissue-restricted expression and heterogeneity of function¹⁴. Recent studies have reported the expression of CD200R1 on microglia, macrophages, dendritic cells and a subpopulation of T cells. Ligation with CD200 negatively regulates immune response through multiple mechanisms including the expansion of myeloid derived suppressor cell (MDSC) populations¹⁵. Defects in the CD200-CD200R pathway contribute have also been reported in neurological diseases such as Multiple Sclerosis, Parkinson's and Alzheimer's diseases^(16, 17). Together, these data led us to hypothesize that brain tumors over-express CD200 relative to healthy brain tissue, and that blocking tumor-derived CD200 would enhance the efficacy of immunotherapy.

Materials and Methods.

Patient Sample Collection

Patients undergoing care for brain tumors were identified and consented prior to surgical biopsy and/or resection. Patients and/or their legal representative were consented according to institutional guidelines. Patients were treated at one of three participating institutions: University of Minnesota, University of Pittsburgh or the University of Colorado. Patient tissue and blood samples were collected and stored for analysis at the University of Minnesota.

Western Analysis

Tissues were minced and sonicated in RIPA lysis buffer containing protease and phosphatase inhibitors (Pierce). Protein concentrations were determined using the bicinchoninic acid colorimetric method (Pierce). Tumor lysates were diluted in reducing sample buffer (Novex) and 50 μg were loaded per lane on a 4% to 12% SDS-PAGE gel (Nu-Page) and run at 160 volts (0.8 volt hours). Gels were then transferred to nitrocellulose at 7 volts (BioRad), blocked using 5% non-fat dry milk/0.05 mM tris buffered saline with 0.05% tween-20 for 1 hr, incubated at 1:1000 in anti-OX2, 200 μg/ml (Santa Cruz) in blocking buffer for 1 hr, and washed six times over 1 hr in TBS/Tween-20. Blots were then incubated at 1:10,000 with anti-goat, 500 μg/0.5 ml IgG HRP (Jackson ImmunoResearch) in blocking buffer for 1 hour and washed six times over 1 hour in TBS/Tween-20. Nitrocellulose was incubated in ECL Plus chemiluminescent substrate (GE) for 1 minute and exposed to HyBlot CL Autoradiography film (Denville Scientific) for 30 seconds.

Microarray Analysis

Data for FIGS. 15A, 20 and 21, transcriptomic microarray profiles of tumor and normal brain tissue samples were generated using Affymetrix HG-U133 Plus 2 GeneChip microarrays (Affymetrix) as previously described¹⁸. RNA was isolated from specimens using RNeasy or DNA/RNA AllPrep kit (Qiagen) according to manufacturer's instructions. Tumor specimens from which both RNA and DNA were isolated were determined by histology to contain ≧70% tumor cells and thus had minimal normal tissue contamination. RNA quality was verified using the Nano Assay Protocol for the 2100 Bioanalyzer (Agilent) (RNA integrity number≧8). RNA was amplified, biotin-labeled, and hybridized to Affymetrix HGU 133 Plus 2 GeneChips according to manufacturer's instructions. Analysis of transcriptomic microarray data was performed using Bioconductor functions written in the R programming language (http://www.bioconductor.org). Microarray data CEL files were background corrected and normalized using the guanine cytosine robust Multiarray Average (gcRMA) algorithm, resulting in log 2 expression values. Normalized hybridization intensity values for CD200 were obtained from this dataset and averaged for each type and molecular subtype of pediatric brain tumor

For FIG. 15B, total RNA was purified from fresh frozen tumor samples previously collected as part of an IRB-approved research protocol using the RNeasy mini kit (Qiagen). cRNA was generated, quantified and hybridized to U133 Plus 2.0 arrays at the UCLA DNA Microarray Facility using standard Affymetrix protocols. CEL files were normalized using GeneSpring GX 11.5.1 software (Agilent Technologies). To evaluate the baseline expression of CD200 in heterogeneous human brain tumor tissues, we analyzed the relative expression of CD200 using microarray gene expression profiling in over 300 human brain tumor samples and segregated the data by known gene expression signatures. The relative expression of CD200 was normalized and tested. CD200 expression was then plotted together with overall survival using the Probeset Analyzer tool developed at UCLA (http://probesetanalyzer.com).

Animal Models and Cell Lines

Tumors were implanted into female C57BL/6 mice (6-8 wk old) (Jackson Laboratory) and maintained in a pathogen-free facility according to the guidelines of the University of Minnesota Animal Care and Use Committee. The GL261 orthotopic transplant model was established in C57BL/6 (B6) mice by inoculation with 15,000 GL261-Luc⁺ cells in 1 μl of saline. Tumors were implanted stereotactically into the right striatum; coordinates were 2.5 mm lateral, 0.5 mm anterior of bregma, and 3 mm deep from the cortical surface of the brain¹⁹. Tumor burden was determined by bioluminescent imaging. Light emitted from the tumors was quantified using Living Image software (Xenogen) and expressed as photons per second per centimeter squared per steradian (p/s/cm²/sr). GL261 cells for tumor lysate vaccines were cultured in neural stem cell media consisting of DMEM/F12 (1:1) with L-glutamine, sodium bicarbonate, penicillin/streptomycin (100 U/ml), B27 and N2 supplements (Life Technologies), and 0.1 mg/ml Normocin (Invivogen). Cultures were maintained at 5% O₂ and supplemented with 20 ng/ml EGF and FGF semiweekly (R&D Systems, Minneapolis, Minn.). The breast carcinoma EMT6 model was established in BALB/c mice by injection of 1×10⁶ EMT6 cells in 50 ml of PBS into the left superior mammary fat pad as described²⁰. Mice were euthanized when tumors reached 1000 mm³. Mice were challenged with 1×10⁶ EMT6 cells in 50 ml of PBS into the left superior mammary fat pad. Tumor cells used to establish both models were cultured in DMEM containing 10% FBS, penicillin/streptomycin (100 U/ml), and 0.1 mg/ml Normocin (Invivogen) in atmospheric oxygen.

CD200R Antagonist

CD200R antagonist: 6059 (NTIGDGGCY), C-A12, c region sequence with an alanine substitution in the 12^(th) amino acid position (VTWQKKKAVSPANM), 4013 (LFNTFGSQKVSGT) and 4004 (TASLRCSLKTSQE) were synthesized by Genscript.

Vaccine Preparation and Injection

Tumor lysates were prepared by dissociating tumor cells with non-enzymatic dissociation solution (Sigma). Cells were then washed 3 times with PBS, re-suspended in 500 μL PBS, and frozen overnight at −80° C. Cells were then lysed by five freeze/thaw cycles of freezing in liquid nitrogen and thawing in a 55° C. water bath. Cell debris was pelleted by centrifugation at 14,000 RCF, and the protein concentration of the supernatant was determined using a Bradford assay. Lysates were stored at −80° C. until use. Each vaccine was prepared on the day of vaccination and consisted of 65 μg of protein tumor lysate and 10 μg Poly:ICLC (Oncovir, Inc.), with or without 50 μg of the 6059 peptide antagonist, in a final volume of 1004 injected intradermally in the back of the neck. For survival studies, vaccines were administered weekly starting three days post-tumor implantation for a total of 6 doses. In T cell priming experiments, CD8 T-cell priming experiments, animals were vaccinated intradermally on four consecutive days with 100 μg Ovalbumin (OVA) and 10 μg Poly:ICLC, and once more on day eleven¹⁹.

Flow Cytometry

Anti-mouse CD8α-Pacific Blue (clone 53-6.7) was purchased from eBioscience. A SIINFEKL/K^(b) dextramer-PE (‘SIINFEKL’ disclosed as SEQ ID NO: 11) was used for detection of SIINFEKL/K^(b)-binding CD8 T-cells (Immunodex) (‘SIINFEKL’ disclosed as SEQ ID NO: 11). For whole blood staining, 50 μL of blood was obtained via retro-orbital bleed and placed in 100 μL in heparin and PBS. 5 μL of SIINFEKL/K^(b) dextramer (‘SIINFEKL’ disclosed as SEQ ID NO: 11) was added to the blood and incubated at room temperature for 10 min. Then 0.5 μg of antibody was added and incubated for an additional 20 min. The red cells were lysed by adding 1 mL of 1:10 dilution lysis buffer (BD Pharmigen), incubated for 10 min, washed twice analysis by flow cytometry. Data analysis was performed using FlowJo software. In our human experiments, peripheral blood mononuclear cells and whole blood for serum were isolated from patients at vaccination and on weeks 4, 8, 12, and 24 post vaccination in a recent clinical trial²¹. A 100 μl sample of whole blood was immediately analyzed for percentage of MDSCs ((Lineage-FITC (CD3, CD14, CD16, CD19, CD20, CD56) CD33-APC, HLA-DR-PerCp)) by flow cytometry. Sera CD200 levels were determined by ELISA (Sino Biological Inc.).

Cytokine Detection

Lymph nodes were homogenized in RPMI media containing 10% FBS, penicillin/streptomycin (100 U/ml), and 0.1 mg/ml Normocin (Invivogen). Cells were filtered using a 70-micron filter, centrifuged and resuspended at a concentration of 500,000 cells/well in triplicate, stimulated with 10 μg of OVA and incubated for 48 hrs. Fifty microliters of supernatant was analyzed for IFN-γ using a flow cytometric bead array according to the manufacturer's protocol (BD Biosciences).

MDSC Detection and Analysis

Spleens were harvested homogenized in RPMI media containing 10% FBS, penicillin/streptomycin (100 U/ml), and 0.1 mg/ml Normocin (Invivogen). Cells were then filtered using a 70-micron filter, centrifuged, and resuspended in 5 ml of Ammonium-Chloride-Potassium buffer and incubated for 5 minutes at room temperature to lyse RBCs. Following lysis, cells were washed and plated into 96 well plates at a concentration of 500,000 cells/well in triplicate. Following 24 h incubation, CD200R antagonist peptide 6059 was added to the appropriate wells, incubated for 20 min prior to adding 5 μg of purified CD200 protein (Sino Biological) and incubated for a further 72 hrs, harvested and analyzed for anti-CD11b and anti-Ly6c population using an LSR II flow cytometer. In separate sets of experiments, 100 μg/well of OVA was added to splenocytes. Following 24 hr incubation, 3×10⁵ purified CD8 T-cells isolated from an OT-I mouse using Miltenyi magnetic bead isolation kit was added to splenocytes and incubated for an additional 48 hrs. Following incubation, 50 μl culture supernatant was analyzed for IFN-γ using a flow cytometric bead array according to the manufacturer's protocol (BD Biosciences). Another 50 μl of culture supernatant was used to determine the Arginase-I concentration using an Arginase-I ELISA kit per manufacturer's instructions (ABNOVA).

To determine the level of MDSC expansion when splenocytes were exposed to tumor cells, splenocytes were also harvested and purified as described above; 300,000 splenocytes were plated in the bottom of 24 well transwell plates containing a 0.4-micron filter. Following 24 hr incubation, 30,000 GL261 cells were plated on the transwell insert with and without the CD200R antagonist 6059. Total volume was 700 μl/well so that the insert was submerged in the media within the wells. Cells were incubated for 5 days, harvested, and stained with CD11b and GR-1 to determine MDSC levels. In another set of wells, OVA was added to the wells 24 hours after the splenocytes were plated. Following another 72 hr incubation, 3×10⁵ purified CD8 T-cells isolated from an OT-I mouse and were added to the wells and incubated for an additional 72 hrs. Supernatant was harvested and used to determine IFN-γ concentration levels by bead array (BD Biosciences).

Statistical Analysis

Statistical comparisons were made by one-way ANOVA (Kruskal-Wallis test) followed by post hoc comparisons by Dunns to compare selected groups. Correlations were determined by linear regression with a 95% confidence level. Differences in animal survival were evaluated by log-rank test. All tests were done with Prism 5.0d software (Graph Pad Software, Inc). P values<0.05 were considered significant.

Results

CD200 is Overexpressed by Many Brain Tumors

Several published reports demonstrate CD200 expression on human gliomas by first examining CD200 expression was found in a variety of human brain tumor tissue samples: anaplastic oligoastrocytoma (n=1), GBM (n=3), meningioma (n=1), ependymoma (n=2), oligodendrogliomas (n=1) and pilocytic astrocytoma (n=1)(FIG. 15A). Given these initial findings, we next compared CD200 mRNA levels in a larger cohort of brain tumors relative to rhabdomyosarcomas, as non-brain tumor controls. We observed an overall statistically significant (p=0.0001) difference in expression between all brain tumor subtypes and rhabdomyosarcoma. These comparisons included anaplastic astrocytoma (n=5), anaplastic oligoastrocytoma (n=3), pilocytic astrocytoma (n=17), oligodendrogliomas (n=4), medulloblastoma (n=31), craniopharyngioma (n=11), diffuse intrinsic pontine glioma (8), GBM (n=31) and primitive neuroectodermal tumor (n=13), (p<0.05, p<0.001, p<0.0001, p<0.001, p<0.0001, p<0.0001, p<0.001, p<0.05 and p=0.0001 respectively) (FIG. 15B). Ependymoma (n=45) failed to reach statistical significance. Interestingly, further analysis of GBMs revealed an increased expression of CD200 in the proneural subtype compared to proliferative (p<0.001), mesenchymal (p<0.0001) and promesenchymal tumors (p<0.0001) (FIG. 15C). In addition, we observed statistically significant increases in the ependymoma supratentorial subset compared to posterior fossa group A and posterior fossa group B (p=0.0001 and p=0.001 respectively). CD200 mRNA levels were also significantly elevated in the group 4 (sonic hedgehog/cMYC negative) medulloblastoma subset compared to sonic hedgehog positive SHH⁺ and group 3 (cMYC⁺) subsets (p=0.001 and p=0.001 respectively) (FIG. 20).

Accordingly, we compared CD200 mRNA expression on a variety of tissues. The data demonstrate an overall statistically significant increase in mRNA transcript levels in normal brain compared to non-brain tissues (p=0.001). We observed increased CD200 expression throughout the brain with the exception of the choroid plexus, which was statistically lower than the rest of the brain combined (v0.005). Post hoc analysis determined a significant increased expression in breast, kidneys and lungs (p<0.001) and pancreas (p<0.0001). Thymus failed to reach statistical significance (FIG. 21A). In addition, post analysis revealed a statistically significant difference between choroid plexus and frontal and temporal lobes (p<0.001 and p<0.05 respectively). Cerebellum, hippocampus, lumbar spinal cord, medulla, midbrain, pons and occipital lobe failed to reach statistical significance (FIG. 21B).

Soluble CD200 Correlates with Lineage Negative MDSC Populations in GBM Patients

Previous studies reported that it is the soluble form of CD200 (sCD200) that correlates with poor patient outcome²⁴. Therefore, we analyzed sera from brain tumor patients for sCD200 levels. We observed a significant difference in sCD200 levels between patients with various brain tumor types by ANOVA (p=0.001). Post analysis revealed a significant increase in sCD200 in patients with glioblastoma multiforme GBM compared to patients with ependymoma (p<0.001) (FIG. 16A).

Interestingly, three patients in the GBM group with the highest concentrations of sCD200 had large aggressive recurrent disease. Furthermore, the highest concentration in the medulloblastoma group was from a patient in the clinical trial²¹ who rapidly went off trial due to tumor progression. Another patient with ependymoma in this same trial had a statistically significant increase in sCD200 (p<0.01 between weeks 4 and 12) as she went off trial due to recurrence (FIG. 22A). Together, our data support the reported correlation between elevated sCD200 and poor prognosis.

One mechanism by which CD200 induces an immune suppressive environment is through the expansion of MDSCs¹⁵. Accordingly, we sought to correlate sCD200 in patients' sera to the percentages of peripheral blood lineage negative MDSCs. The patients were all participants in a recent clinical trial designed to test the safety of our allogeneic vaccine²¹ and included those with ependymoma (n=1) and GBM (n=3); correlations between sCD200 in the sera and MDSC frequencies were made just prior to vaccination, and at 4, 8, and 12 weeks post-vaccination²¹. There were significant correlations between sCD200 and expansion of MDSCs in the GBM patients (FIG. 16B; R²=0.99) and ependymoma patient (FIG. 22B; R²=0.97). These data demonstrate a direct correlation between sCD200 and MDSC expansion.

CD200 Pathway Blockade Reduces Immune Suppression Induced by sCD200

Based on the work of Gorczynski et al²⁵, we synthesized CD200R antagonist peptides (6059) that reportedly outcompetes the intact CD200 protein for binding to the CD200R²⁵. The addition of GL261 glioma tumor cells induced a significant expansion of CD11b⁺Gr1⁺ MDSC (p<0.01) and suppressed the ability of purified OT-I CD8 T-cells to respond to OVA stimulation (p<0.01) (FIG. 17A). Excitingly, the addition of the CD200R antagonist blocked both the expansion of MDSCs as well as the production of IFN-γ (p<0.01 and p<0.01 respectively) (FIG. 17A).

To determine if MDSC expansion is due to CD200, naïve splenocytes were pulsed with purified recombinant CD200 protein with or without the CD200R antagonist. These experiments show that CD200 alone significantly expanded the MDSC population (p<0.01). Pre-incubating cells with the CD200R antagonist significantly blocked CD200 induced MDSC expansion (p<0.01) (FIG. 17B). In addition, the CD200R antagonist blocked CD200 induced arginase-I secretion (p<0.01) (3B).

CD200R Antagonist Blocks Tumor Induced Suppression Resulting in an Extension in Survival Glioma Bearing Mice

We previously reported that vaccinating GL261 glioma bearing mice near the sentinel (cervical) lymph nodes failed to elicit an effective tumoricidal response¹⁹. In addition, we demonstrated as described above that glioma cells have the ability to enhance a MDSC population (FIG. 17A). Therefore, we investigated the ability of our CD200R antagonist to block/reverse the in vivo suppressive effects of sCD200. Tumor bearing and non-tumor bearing mice were vaccinated in the back of the neck with OVA+Poly:ICLC to induce an antigen specific cellular immune response. The data presented in FIGS. 18A&B show that the percentage of OVA specific SIINFEKL (SEQ ID NO: 11) binding CD8⁺ T-cells (p<0.01) as well as the ability to induce TNFα and IFNγ is significantly suppressed (p<0.001 and p<0.01 respectively) in OVA primed GL261 bearing mice (white bars) compared to non tumor-bearing mice (black bars). To investigate the potential role of CD200 in GL261 glioma induced immune suppression, we incorporated the CD200R antagonist 6059 into our vaccine inoculum. Tumor-bearing mice treated with the CD200 antagonist one day prior to and concurrently with OVA vaccine had increased numbers of SIINFEKL-specific CD8 T-cells (‘SIINFEKL’ disclosed as SEQ ID NO: 11) compared to mice vaccinated without the antagonist (p<0.01) (FIG. 18A). Moreover, lymphocytes isolated from the cervical lymph nodes of mice vaccinated with the addition of the CD200R antagonist had significantly enhanced TNFγ and IFNγ production (p<0.01 and p<0.001, respectively)(FIG. 18B). These experiments suggest that CD200 plays a role in suppressing the immune responses in GL261 tumor bearing mice.

We next investigated whether the CD200R antagonist could enhance survival in our GL261 mouse model. We inoculated the CD200R antagonist one day prior to and concomitantly with vaccination. We observed a statistically significant inhibition of tumor growth in mice vaccinated with antagonist compared to mice vaccinated with tumor lysates alone (p<0.001) and mice that received saline only as a control (FIG. 18C). The addition of the CD200R antagonist with the vaccine significantly slowed tumor growth (p<0.01), resulting in enhanced survival benefit (p<0.01) compared to other treatment groups (FIGS. 18C&D).

CD200R Antagonists Enhance Survival in Glioma and Breast Carcinoma Models

Gorczynski reported that multiple regions of the CD200 act as antagonist blocking the suppressive effects of CD200²⁵. Ongoing investigations of another CD200R antagonist (C-A12)²⁶ demonstrates even greater survival (p<0.001) (FIG. 19B) compared to the 6059 in our GL261 glioma model. In addition, to test if our antagonist was efficacious in a non-CNS tumor, we tested multiple CD200 antagonists on our breast carcinoma model. CD200R antagonists 4004 and 4013 showed enhanced survival benefit in an EMT6 breast carcinoma model (FIG. 19B). Interestingly, CD200R 4013 and 4004 failed to confer survival in our glioma model (data not shown). All mice were tumor free by day 100 when they were challenged with 1×10⁶ EMT6 cells. Regardless of the CD200R antagonist used, all mice rejected challenge without further vaccinations. These experiments demonstrate the ability of small molecule peptides as pathway blockade inhibitors to mitigate the negative signals of the CD200/CD200R interaction.

DISCUSSION

Because of the myriad of ways tumors induce immunosuppression, it is unlikely that any single monotherapy will be completely effective. Therapy using a combination of vaccines, adoptive cell therapy, checkpoint inhibitors and other immune stimulating therapies will likely have even better results. Because of this, several immunotherapeutic approaches, such as agents targeting the known immune checkpoints, have been developed and are under evaluation as cancer interventions.²⁷⁻²⁹ We find significantly increased levels of CD200 mRNA in multiple human brain tumors as well as increased soluble CD200 (sCD200) levels in the sera of patients. A CD200 antagonist peptide mitigated glioma-induced immune suppression in mice. The combination of this peptide and a glioma-derived vaccine significantly extended survival in glioma-bearing mice. Our data suggest that gliomas have co-opted CD200-mediated immune suppression to persist, and that blocking the CD200/CD200R immune checkpoint is a viable strategy for glioma therapy.

Our proteomic data show that the immunosuppressive molecule CD200 (OX2) is enriched in the cerebral spinal fluid and tumor-draining (cervical) lymph nodes in GL261-bearing mice. CD200 is expressed on multiple cells, including neurons, directly interacting with immune cells to down regulate pro-inflammatory responses. We believe that the soluble form of CD200 (sCD200) derived from tumors is carried to the cervical lymph nodes through the cerebral spinal fluid, inducing negative signals by placing severe limitations on the ability of the immune system to mount a tumoricidal response following vaccination.

In contrast to non-CNS tissues, we detected high expression levels of CD200 throughout the brain with the exception of the choroid plexus (FIGS. 20A&B). Therefore, it was not surprising that brain tumors, due to the origin of the cells, had higher expression of CD200 compared to a non-CNS tumor (FIG. 15B). However, CD200 expression not only varies within different tumors, specific tumor subsets also have various expression levels of CD200. We demonstrated a statistically significant increase in CD200 expression on proneural subsets of GBM compared to mesenchymal GBM. This is interesting since the proneural subset is associated with minimal immune cell infiltrate, limiting immune-tumor cell interactions. However, patients with the proneural subset of GBM have a more favorable prognosis than the mesenchymal subset, which is associated with high cell infiltrates. This may be due to the low accumulation of MDSCs or M2 type macrophages that enhancing tumor growth³⁰. The same trend may be true for ependymoma and medulloblastoma subsets, posterior fossa A and group 3 (cMYC⁺) subgroups. respectively, which are more aggressive, low CD200 expression (FIG. 21) and high immune infiltrates^(31, 32, 33).

CD200 is expressed on multiple immune cells negatively regulating cells through the CD200 receptor¹⁵. CD200/CD200R interactions result in the expansion of suppressive cell populations such as myeloid derived suppressor cells (MDSC)³⁴. In our studies, we observed a positive correlation between soluble CD200 concentration and lineage negative MDSC expansion in both our GBM and ependymoma immunotherapy patients as they progressed and went off trial (FIG. 16B and FIG. 22B respectively). These studies demonstrate a direct correlation between sCD200 and the expansion of the suppressive cells. However, we recognize that this study has a low number of patients. Although studies are ongoing to support our observations in humans, we have demonstrated that sCD200 induces expansion of MDSCs in our murine glioblastoma model.

To overcome the immunosuppressive nature of tumors, agents targeting the known immune checkpoints (checkpoint inhibitors) have been developed and are under evaluation as cancer interventions²⁷⁻²⁹. These inhibitors, in combination with current immunotherapy regimens, remarkably enhance the efficacy of anti-tumor immunotherapy. Checkpoint inhibitors utilize mechanisms of blocking the interactions between ligands and their receptors. Two humanized antibodies, ipilimumab and nivolumab³⁵, have been developed as checkpoint inhibitors to block negative signals to T cells. Our data demonstrate that CD200R antagonist peptides reverse/block GL261-derived immune suppression within tumor-draining lymph nodes. This reversal is striking given the aggressiveness of GL261 and the many ways it suppresses the immune system, suggesting CD200 is a central driver of glioma-mediated immune suppression.

Our current hypothesis is that the CD200R antagonists bind to CD200R on local dendritic cells protecting them from the suppressive effects of soluble CD200 upon entry into the draining lymph nodes. This hypothesis was determined from preliminary data demonstrating that vaccinating mice with the CD200 antagonist significantly enhanced the expansion of a SIINFEKL/CD8 T cell population (FIG. 17a ) (‘SIINFEKL’ disclosed as SEQ ID NO: 11). However, early studies revealed that mice had to be pre-vaccinated with the antagonist prior to tumor lysate vaccination to achieve a survival benefit. We believe that this was due to the presence of sCD200 within our tumor lysates competing for the CD200R on dendritic cells.

Being we have only observed a 10% survival benefit thus far and are examining whether using alanine substitutions to our peptide antagonists could increase binding and enhance survival_(—) Excitingly, an antagonist from the C region with an alanine substitution showed significantly enhanced survival in our glioma model (FIG. 19A). Other CD200 antagonist peptides are currently being investigated as well.

The data presented here are significant and are a part of a more comprehensive study to further understand the effects of CD200 in cancer. Mechanistic studies are ongoing and not within the scope of this manuscript. Nevertheless, we demonstrate the potential importance of CD200 in tumor immunotherapy and the use of antagonist peptides as a means to block the suppressive effects of sCD200 to enhance immunotherapy not only for glioma, but for breast carcinoma as well. We anticipate that our results will lead to the development of novel inhibitors of the CD200R pathway that can be used in immunotherapy to mitigate the suppressive tumor environment in a variety of human cancers.

Example 3 References

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Gene expression profile     correlates with T-cell infiltration and relative survival in     glioblastoma patients vaccinated with dendritic cell immunotherapy.     Clin Cancer Res 2011; 17(6): 1603-15. -   6. Okada H, Kalinski P, Ueda R, et al. Induction of CD8+ T-cell     responses against novel glioma-associated antigen peptides and     clinical activity by vaccinations with {alpha}-type 1 polarized     dendritic cells and polyinosinic-polycytidylic acid stabilized by     lysine and carboxymethylcellulose in patients with recurrent     malignant glioma. J Clin Oncol 2011; 2011: 330-36. -   7. Kerkar S P, Restifo N P. Cellular constituents of immune escape     within the tumor microenvironment. Cancer Res 2012; 72(13): 3125-30. -   8. Anandkumar A, Devaraj H. Tumour immunomodulation: mucins in     resistance to initiation and maturation of immune response against     tumours. Scand J Immunol 2013; 78(1): 1-7. -   9. Callahan M K, Wolchok J D. At the bedside: CTLA-4- and     PD-1-blocking antibodies in cancer immunotherapy. J Leukoc Biol     2013; 94(1): 41-53. -   10. Curran M A, Montalvo W, Yagita H, Allison J P. PD-1 and CTLA-4     combination blockade expands infiltrating T cells and reduces     regulatory T and myeloid cells within B16 melanoma tumors. Proc Natl     Acad Sci USA 2010; 107(9): 4275-80. -   11. Chitnis T, Imitola J, Wang Y, et al. Elevated neuronal     expression of CD200 protects Wlds mice from inflammation-mediated     neurodegeneration. Am J Pathol 2007; 170(5): 1695-712. -   12. Koning N, Swaab D F, Hoek R M, Huitinga I. Distribution of the     immune inhibitory molecules CD200 and CD200R in the normal central     nervous system and multiple sclerosis lesions suggests neuron-glia     and glia-glia interactions. J Neuropathol Exp Neurol 2009; 68(2):     159-67. -   13. Hoek R M, Ruuls S R, Murphy C A, et al. Down-regulation of the     macrophage lineage through interaction with OX2 (CD200). Science     2000; 290(5497): 1768-71. -   14. Holmannova D, Kolackova M, Kondelkova K, Kunes P, Krejsek J,     Andrys C. CD200/CD200R paired potent inhibitory molecules regulating     immune and inflammatory responses; Part I: CD200/CD200R structure,     activation, and function. Acta Medica (Hradec Kralove) 2012; 55(1):     12-7. -   15. Gorczynski R, Chen Z, Kai Y, Lee L, Wong S, Marsden P A. CD200     is a ligand for all members of the CD200R family of immunoregulatory     molecules. J Immunol 2004; 172(12): 7744-9. -   16. Koning N, Bo L, Hoek R M, Huitinga I. Downregulation of     macrophage inhibitory molecules in multiple sclerosis lesions. Ann     Neurol 2007; 62(5): 504-14. -   17. Walker D G, Dalsing-Hernandez J E, Campbell N A, Lue L F.     Decreased expression of CD200 and CD200 receptor in Alzheimer's     disease: a potential mechanism leading to chronic inflammation. Exp     Neurol 2009; 215(1): 5-19. -   18. Donson A M, Birks D K, Barton V N, et al. Immune gene and cell     enrichment is associated with a good prognosis in ependymoma. J     Immunol 2009; 183(11): 7428-40. -   19. Ohlfest J R, Andersen B M, Litterman A J, et al. Vaccine     injection site matters: qualitative and quantitative defects in CD8     T cells primed as a function of proximity to the tumor in a murine     glioma model. J Immunol 2013; 190(2): 613-20. -   20. Xiong Z, Gharagozlou S, Vengco I, Chen W, Ohlfest J R. Effective     CpG immunotherapy of breast carcinoma prevents but fails to     eradicate established brain metastasis. Clin Cancer Res 2008;     14(17): 5484-93. -   21. Olin M, Low W, McKenna D, et al. Vaccination with Dendritic     Cells Loaded with Allogeneic Brain Tumor Cells for Recurrent     Malignant Brain Tumors Induce a CD4+IL17+Response. J Immunother     Cancer 2014; 2: 4. -   22. Petermann K B, Rozenberg G I, Zedek D, et al. CD200 is induced     by ERK and is a potential therapeutic target in melanoma. 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Example 4

Mice were vaccinated as described in FIG. 4 with peptide inhibitor P1A12. Blood from mice vaccinated with tumor lysate+CpG or tumor lysate+CpG+inhibitor were analyzed for MDSC expansion (FIG. 23). It was observed that CD200 inhibitor inhibited MDSC expansion in vivo. CD11b cells isolated for wild type or CD200 receptor knock out mice were pulsed with OVA+Poly:ICLC+/−P1A12 inhibitor, and scrambled inhibitor was used as a control (FIG. 24). Cells were washed and OT-I Cells were added. Supernatants were analyzed for IFN gamma following 48 hour incubation. It was observed that CD200 inhibitor acted as an agonist for the CD200 receptor.

Non-tumor bearing mice were vaccinated saline, tumor lysate or inhibitor (FIG. 25). Twenty four hours later, mice were vaccinated with A) Saline B) Tumor lysate (TL)+CpG or C) Tumor lysate+CpG+agonist. Six hours later, injection site (skin) was harvested and analyzed for lymphocyte infiltration. D. Lymphocytes within 8 layers of skin/treatment groups were counted to determine enhanced lymphocyte infiltration. Results are set forth in FIG. 26. It was observed that CD200 inhibitor enhanced Chemotaxis.

Purified CD11b cells were pulsed with OVA or OVA+inhibitor. Cells were harvested 48 hours later and analyzed for HLA-DR and co-stimulation markers CD80 and CD86 expression (FIG. 27). It was observed that CD200 inhibitor enhances Co-Stimulatory molecule expression.

Although the foregoing specification and examples fully disclose and enable the present invention, they are not intended to limit the scope of the invention, which is defined by the claims appended hereto.

All publications, patents and patent applications are incorporated herein by reference. While in the foregoing specification this invention has been described in relation to certain embodiments thereof, and many details have been set forth for purposes of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein may be varied considerably without departing from the basic principles of the invention.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 

What is claimed is:
 1. A conjugate comprising at least one CD200 inhibitor operably linked to an adjuvant.
 2. The conjugate of claim 1, wherein the CD200 inhibitor is a peptide having a length of 5 to 20 amino acids.
 3. The conjugate of claim 2, wherein the peptide is 90% identical to amino acid sequence SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:8 or SEQ ID NO:9.
 4. The conjugate of claim 1, wherein the adjuvant is a toll-like receptor (TLR) ligand.
 5. The conjugate of claim 4, wherein the adjuvant is a CpG ODN, Annexin A2, or Poly ICLC, or a fragment thereof.
 6. The conjugate of claim 5, wherein the adjuvant is a fragment Annexin A2, and the fragment of Annexin A2 is the first 12-100 amino acid residues of the N-terminus of Annexin A2.
 7. The conjugate of claim 5, wherein the adjuvant is a fragment Annexin A2, and the fragment of Annexin A2 is the first 15 amino acid residues of the N-terminus of Annexin A2.
 8. The conjugate of claim 5, wherein the adjuvant is MSTVHEILCKLSLEG (SEQ ID NO: 10).
 9. The conjugate of claim 1, wherein the adjuvant is linked to the CD200 inhibitor by means of a covalent bond or by means of a linking group.
 10. A composition comprising the conjugate of claim 1 and a pharmaceutically acceptable carrier or diluent.
 11. The composition of claim 10, further comprising at least one additional CD200 inhibitor.
 12. The composition of claim 10, further comprising a cancer vaccine.
 13. The composition of claim 12, wherein the cancer vaccine is a tumor lysate that is substantially devoid of CD200.
 14. The composition of claim 10, further comprising a second adjuvant not linked to the conjugate.
 15. A method of treating a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to an animal in need thereof a therapeutic regimen comprising a composition of claim
 10. 16. The method of claim 15, further comprising administering a chemotherapy agent.
 17. A method of reversing or modulating immune suppression in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition of claim
 10. 18. A method of reversing or modulating immune suppression in a tumor microenvironment or sentinel lymph nodes in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition of claim
 10. 19. A method of enhancing efficacy of a cancer vaccine in a patient having a disease or disorder arising from abnormal cell growth, function or behavior, which method comprises administering to a patient in need thereof a composition of claim
 10. 20. A kit for treating cancer, comprising: (a) a first pharmaceutical composition comprising a composition of claim 10; and (b) instructions for use. 